Brita Lp v. Itc

Case: 24-1098   Document: 85    Page: 1     Filed: 10/15/2025




   United States Court of Appeals
       for the Federal Circuit
                 ______________________

                      BRITA LP,
                       Appellant

                           v.

      INTERNATIONAL TRADE COMMISSION,
                  Appellee

      VESTERGAARD FRANDSEN INC., D/B/A
   LIFESTRAW, KAZ USA, INC., HELEN OF TROY
                   LIMITED,
                   Intervenors
             ______________________

                       2024-1098
                 ______________________

    Appeal from the United States International Trade
 Commission in Investigation No. 337-TA-1294.
                 ______________________

                Decided: October 15, 2025
                 ______________________

     DEANNE MAYNARD, Morrison & Foerster LLP, Wash-
 ington, DC, argued for appellant. Also represented by
 SETH W. LLOYD; PAUL ASHLEY AINSWORTH, Sterne Kessler
 Goldstein & Fox PLLC, Washington, DC.

    PANYIN HUGHES, Office of the General Counsel, United
 States International Trade Commission, Washington, DC,
 argued for appellee. Also represented by HOUDA MORAD.
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 2                                              BRITA LP v. ITC




     ADAM SWAIN, Alston & Bird LLP, Washington, DC, ar-
 gued for all intervenors. Intervenors KAZ USA, Inc., Helen
 of Troy Limited also represented by THOMAS WILLIAM
 DAVISON; KIRK T. BRADLEY, KARLEE N. WROBLEWSKI, Char-
 lotte, NC; KATHERINE RUBSCHLAGER, San Francisco, CA.

     JEFFREY R. GARGANO, K&L Gates LLP, Chicago, IL, for
 intervenor Vestergaard Frandsen Inc. Also represented by
 DEVON C. BEANE, Alston & Bird LLP, Chicago, IL.
                  ______________________

      Before PROST, REYNA, and CHEN, Circuit Judges.
 PROST, Circuit Judge.
     Brita LP (“Brita”) appeals from a United States Inter-
 national Trade Commission (“Commission”) decision deter-
 mining claims 1–6 and 23 of 

U.S. Patent No. 8,167,141

 (“the ’141 patent”) invalid for lack of written description,
 lack of enablement, and indefiniteness. For the following
 reasons, we affirm as to lack of written description and lack
 of enablement.
                         BACKGROUND
                               I
     The ’141 patent is titled “Gravity Flow Filter” and is-
 sued on May 1, 2012. ’141 patent Title (capitalization nor-
 malized). The application for the ’141 patent was filed as
 a continuation-in-part on September 9, 2008 based on sev-
 eral other applications, each of which Brita abandoned.
 The ’141 patent, similar to its predecessor applications, is
 directed to gravity flow fluid filtration systems used for re-
 moving contaminants from water. 

Id.

 at col. 1 ll. 15–18. It
 claims “filter media including at least activated carbon and
 a lead scavenger.” 

Id.

 at claim 1. Activated carbon is used
 “to generally improve the taste and odor of the water,” 

id.

 at col. 1 ll. 58–61, and is typically used together with an
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 BRITA LP v. ITC                                              3



 additive to facilitate the removal of heavy metals, such as
 lead and copper, 

id.

 at col. 3 ll. 51–57. The ’141 patent ex-
 plains that activated carbon may be used with a “lead scav-
 enger,” which is “for removing lead from water.” 

Id.

 at col.
 11 ll. 60–65.
     The sole independent claim at issue, claim 1, recites:
     A gravity-fed water filter, comprising:
     filter media including at least activated carbon and
     a lead scavenger;
     wherein the filter achieves a Filter Rate and Per-
     formance (FRAP) factor of about 350 or less accord-
     ing to the following formula:
                                 [𝑉𝑉 ∗ 𝑓𝑓 ∗ 𝑐𝑐𝑒𝑒 ]
                      𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 =
                                    [𝐿𝐿 ∗ 2]
     where:
     V=volume of the filter media (cm3),
     f=average filtration unit time over lifetime L
     (min/liter),
     ce=effluent lead concentration at end of lifetime L
     when source water having a pH of 8.5 contains 90–
     120 ppb (µg/liter) soluble lead and 30–60 ppb (µg/li-
     ter) colloidal lead greater than 0.1 µm in diameter,
     and
     L=filter usage lifetime claimed by a manufacturer
     or seller of the filter (gallons).
      The ’141 patent identifies various types of filter media,
 including carbon blocks, mixed media, membranes,
 nonwovens, depth media, nanoparticles and nanofibers,
 and ligands. 

Id.

 at col. 25 ll. 9–12, col. 26 ll. 30–37. These
 filter media have different characteristics and face differ-
 ent challenges associated with their use in filtering water.
 For example, carbon blocks use activated carbon held to-
 gether with a binder, while loose or mixed media use
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 4                                                 BRITA LP v. ITC




 granular activated carbon packed into a compartment
 without a binder. For carbon blocks, “lead-reducing
 sorbents” can be blended with the carbon particles and the
 binder particles. 

Id.

 at col. 2 ll. 38–39, col. 11 ll. 60–65. For
 other types of media, an additive, such as ion exchange
 resin, can be mixed with carbon to help the filter reduce
 lead. 

Id.

 at col. 3 ll. 24–38; see also 

id.

 at col. 26 ll. 30–34.
 One problem with mixed media filters is that “they require
 a long contact time to work properly, which limits the flow
 rate,” and “they take up a large amount of space inside the
 filter.” 

Id.

 at col. 3 ll. 51–63; see also 

id.

 at col. 3 ll. 64–67
 (“A further problem associated with blended media of gran-
 ular carbon and ion exchange resin is that they have lim-
 ited contaminant removal capability due to particle size
 and packing geometry of the granules.”).
     The ’141 patent expresses a desire to achieve a suitable
 tradeoff of competing requirements for filter performance.
 

Id.

 at col. 5 ll.19–20. Achieving the right balance is im-
 portant because users “do not want to wait a long time for
 the filtered water” and do not want the filter to take up
 excessive space in their home. 

Id.

 at col. 4 ll. 41–50. At the
 same time, a filter should achieve “effective contaminant
 removal and long filter life.” 

Id.

 at col. 4 ll. 50–56. The
 patent explains, however, that adjusting the characteris-
 tics of a filter to achieve good filter performance is not
 straightforward. For example, configuring a filter to have
 a low pressure drop to achieve a fast flowrate is at odds
 with the design goals of “effective contaminant removal
 and long life.” 

Id.

 at col. 4 ll. 52–61. “It would be useful to
 have gravity flow filters that exhibit both good water flow
 rates and high contaminant reduction.” 

Id.

 at col. 5 ll. 19–
 20.
      The ’141 patent characterizes filters in terms of a per-
 formance metric that it calls “Filter Rate and Performance
 Factor (FRAP) Factor.” 

Id.

 at col. 25 ll. 13–17. “Preferred
 filters have a FRAP Factor ranging from 0–350.” 

Id.

 at col.
 25 ll. 17–19. “The nature of the filter meeting [this]
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 BRITA LP v. ITC                                             5



 performance criteria is independent of the exact embodi-
 ment of the filter and thus applicable to mixed-media, car-
 bon blocks, nonwovens, hollow fibers and other filtration
 formats.” 

Id.

 at col. 25 ll. 9–12. Claim 1 requires a FRAP
 factor “of about 350 or less.” 

Id.

 at col. 34 ll. 9–11.
     The only type of filter disclosed in the ’141 patent as
 meeting the claimed FRAP factor of 350 or less is carbon
 block. All of the figures of filters in the patent depict car-
 bon blocks, not any other type of filter media. 

Id.

 at Figs.
 1–20B. The ’141 patent also states:
     Several gravity fed carbon blocks and mixed media
     filters have been tested for flow rate and lead re-
     duction capability against the defined lead chal-
     lenge water.       Filters tested include several
     formulations of carbon blocks along with commer-
     cially available mixed media filters produced by
     BRITA® and PUR®. Based on the results from
     testing, the FRAP factors were calculated for each
     filter and reported below. No mixed media filters
     tested met the claimed FRAP factor range due to
     their inability to remove particulate lead. The for-
     mulations of gravity fed carbon blocks disclosed are
     unique in [their] ability to meet the required FRAP
     factor. The “Examples” below include many exam-
     ples of gravity flow carbon blocks that have a FRAP
     factor of less than 350. It is not believed that any
     currently-marketed gravity-flow filters have a
     FRAP factor of less than 350.
 

Id.

 at col. 26 l. 55–col. 27 l. 2. The “examples” mentioned
 in this paragraph refer to specific formulations of carbon-
 block filters provided in the ’141 patent as well as certain
 “mixed media filters” identified as “the current BRITA®
 gravity-flow mixed media filter, the BRITA® Germany
 MAXTRA® gravity-flow mixed media filter, and the Proc-
 tor and Gamble PUR® 2-stage gravity-flow filter with
 pleated microfilter.” See 

id.

 at col. 27 l. 14–col. 33 l. 12.
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 6                                               BRITA LP v. ITC




      Various characteristics of carbon-block filters, such as
 geometry and chemistry, affect their filtration perfor-
 mance. For example, the use of particular formulations of
 binders in carbon blocks enables “maximizing the available
 surface area of the carbon” which allows for “a carbon block
 that is hydrophilic and readily absorbs water.” 

Id.

 at
 col. 14 ll. 39–41. “Typical carbon block filters” have flow
 rates that are “unacceptably slow,” 

id.

 at col. 11 ll. 26–31,
 but “according to embodiments of the invention,” formula-
 tions of carbon blocks could be made having “excellent pres-
 sure drop” (and thus, fast flow rate) as a result of the “block
 shapes and the porosity and high amount of interstitial
 spaces and passages through the solid profile.” 

Id.

 at
 col. 14 l. 61–col.15 l. 6. The ’141 patent does not disclose
 any specific filter formulation using a filter media other
 than carbon block that achieves the claimed FRAP factor.
                               II
     On December 27, 2021, Brita filed a complaint with the
 Commission under section 337, alleging that various re-
 spondents, including Kaz USA, Inc., Helen of Troy Limited,
 and Vestergaard Frandsen Inc. (together, “Intervenors”),
 imported and sold water filters that infringed various
 claims of the ’141 patent. The Commission initiated its in-
 vestigation on January 31, 2022.
     After a Markman hearing, the administrative law
 judge (“ALJ”) construed “filter usage lifetime claimed by a
 manufacturer or seller of the filter” to mean “[t]he total
 number of gallons of water that a manufacturer or seller
 has validated can be filtered before the filter is replaced,”
 and rejected respondents’ arguments that the limitation is
 indefinite. Certain High-Performance Gravity-Fed Water
 Filters & Prods. Containing the Same, Inv. No. 337-TA-
 1294, 

2022 WL 3357878

, at *2, 12–16 (July 20, 2022). The
 ALJ then issued her initial determination (“ID”), which de-
 termined that there was a violation of section 337. Initial
 Determination, Inv. No. 337-TA-1294, 

2023 WL 2644291

,
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 BRITA LP v. ITC                                                7



 at *1 (Feb. 28, 2023). As relevant here, the ALJ determined
 that asserted claims 1–6 and 23 met the written descrip-
 tion and enablement requirements. 

Id. at *135

, 165–66.
      On the respondents’ petition for review, the Commis-
 sion agreed to review the ALJ’s conclusions concerning:
 (1) the construction of “filter usage lifetime claimed by a
 manufacturer or seller of the filter” and her determination
 that the term was not indefinite; (2) written description;
 and (3) enablement. Certain High-Performance Gravity-
 Fed Water Filters & Prods. Containing the Same, Inv.
 No. 337-TA-1294, 

2023 WL 6290623

, at *3 (Sep. 22, 2023)
 (“Commission Opinion”). The Commission determined
 that (1) the term “filter usage lifetime claimed by a manu-
 facturer or seller of the filter” is indefinite; (2) the asserted
 claims are invalid for lack of written description as to any
 filter media meeting the claimed FRAP factor other than
 carbon-block filters; and (3) the asserted claims are non-
 enabled as to non-carbon-block filters. 

Id. at *17, *38

.
 Given these conclusions, the Commission reversed the ID’s
 finding of a violation of section 337. 

Id. at *38

.
     Brita timely appealed.      We have jurisdiction under
 

28 U.S.C. § 1295

(a)(6).
                          DISCUSSION
     We review the Commission’s legal determinations de
 novo and its factual findings for substantial evidence.
 Guandong Alison Hi-Tech Co. v. ITC, 

936 F.3d 1353, 1358

 (Fed. Cir. 2019). Substantial evidence is “such relevant ev-
 idence as a reasonable mind might accept as adequate to
 support a conclusion.” Consol. Edison Co. v. NLRB, 

305 U.S. 197, 229

 (1938). Importantly, “the possibility of draw-
 ing two inconsistent conclusions from the evidence does not
 prevent an administrative agency’s finding from being sup-
 ported by substantial evidence. Consolo v. Fed. Mar.
 Comm’n, 

383 U.S. 607, 620

 (1966).
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 8                                              BRITA LP v. ITC




     On appeal, Brita challenges the Commission’s determi-
 nations regarding: (1) written description, (2) enablement,
 and (3) indefiniteness. We address each issue in turn.
                               I
     We begin with written description. Section 112 of the
 Patent Act contains a written description requirement dis-
 tinct from the enablement requirement. 

35 U.S.C. § 112

 ¶ 1 (pre-AIA); see Ariad Pharm., Inc. v. Eli Lilly & Co.,
 

598 F.3d 1336, 1340

 (Fed. Cir. 2010) (en banc). To satisfy
 written description, the disclosure of the application must
 “reasonably convey[] to those skilled in the art that the in-
 ventor had possession of the claimed subject matter as of
 the filing date.” Ariad, 

598 F.3d at 1351

. Assessing such
 “possession as shown in the disclosure” requires “an objec-
 tive inquiry into the four corners of the specification from
 the perspective of a person of ordinary skill in the art.” 

Id.

 “[T]he specification must describe an invention under-
 standable to [a person of ordinary skill in the art] and show
 that the inventor actually invented the invention claimed.”
 

Id.

 A “mere wish or plan” for obtaining the claimed inven-
 tion is not adequate written description. Regents of the
 Univ. of Cal. v. Eli Lilly & Co., 

119 F.3d 1559, 1566

 (Fed. Cir. 1997).
      Whether the asserted claims of the ’141 patent lack
 written description support is a question of fact that we re-
 view for substantial evidence. Rivera v. ITC, 

857 F.3d 1315, 1319

 (Fed. Cir. 2017). Here, the asserted claims
 cover any filtration media type with activated carbon and
 a lead scavenger that meet the functional FRAP factor lim-
 itation. As discussed below, substantial evidence supports
 the Commission’s determination that the asserted claims
 lack written description support as to any filter media
 meeting the claimed FRAP factor other than carbon-block
 filters.
     The Commission found that the specification “only pro-
 vides examples of ‘gravity flow carbon blocks that have a
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 BRITA LP v. ITC                                              9



 FRAP factor of less than 350.’” Commission Opinion, 

2023 WL 6290623

, at *21 (quoting ’141 patent col. 26 ll. 63–67).
 We agree. While broadly claiming any “filter media includ-
 ing at least activated carbon and a lead scavenger; wherein
 the filter achieves a [FRAP] factor of about 350 or less,”
 ’141 patent claim 1, the specification describes only a single
 type of filter media that can meet the claimed FRAP fac-
 tor—carbon block. The ’141 patent provides a number of
 “examples” of the “formulations” of filters that were tested
 to obtain a FRAP factor. ’141 patent col. 27 l. 14–col. 28
 l. 2, Table 1. Table 5 of the ’141 patent demonstrates that
 among the filters tested, carbon-block filters were the only
 filter that met the claimed FRAP factor of 350 or less. 

Id.

 at col. 33 ll. 16–22, Table 5. Thus, the only working exam-
 ples of filters meeting the claimed FRAP factor disclosed in
 the ’141 patent are those using carbon-block filter media.
      Further, the specification only provides the details of
 specific formulations of filter components (e.g., lead
 sorbent, carbon, and binder) for carbon blocks, 

id.

 at col. 27
 l. 14–col. 28 l. 47, and the only types of filters that are il-
 lustrated in the figures are carbon blocks. On the other
 hand, the tested “mixed media filters fall above the pre-
 ferred FRAP range (0–350).” 

Id.

 at col. 33 ll. 24–25; see also
 

id.

 at col. 26 ll. 61–63 (“No mixed media filters tested met
 the claimed FRAP factor range due to their inability to re-
 move particulate lead.”); 

id.

 at col. 31 ll. 54–55 (“All mixed
 media filters tested fail to adequately reduce total led con-
 centrations . . . .”).
     The Commission cited testimony from both sides’ ex-
 perts confirming that the ’141 patent provides working ex-
 amples only of carbon-block filters, and no working
 examples of any non-carbon-block filters. Commission
 Opinion, 

2023 WL 6290623

, at *20. The inventors them-
 selves also testified that they did not invent any non-car-
 bon-block filters that would meet the claimed FRAP factor.
 

Id. at *22

. Dr. Elizabeth Knipmeyer, one of the inventors,
 testified that in addressing the issue of removing
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 10                                              BRITA LP v. ITC




 particulate lead in water filters without sacrificing flow
 rates, her group “changed technology from a granular me-
 dia to a carbon block.” J.A. 32707–08 (Dr. Knipmeyer’s
 deposition testimony); see also J.A. 22202 (Dr. Knipmeyer’s
 testimony at evidentiary hearing).
      The Commission also found that, as far as filters meet-
 ing the required FRAP factor, “[b]y their own admission in
 the patent, the inventors were only in possession of a filter
 that uses carbon blocks, not other types of filter media.”
 Commission Opinion, 

2023 WL 6290623

, at *21. Again, we
 agree. The specification states that “[t]he formulations of
 gravity fed carbon blocks disclosed are unique in [their]
 ability to meet the required FRAP factor.” ’141 patent col.
 26 ll. 63–65. The properties that make carbon blocks
 “unique” are evident from other portions of the specifica-
 tion, where the ’141 patent describes the benefits of carbon
 blocks while identifying the “drawbacks,” “problems,” and
 “disadvantages” of other filter media. See, e.g., 

id.

 at col. 3
 l. 57–col. 4 l. 24. Notably, the ’141 patent purports to con-
 figure carbon-block filters in such a way that addresses is-
 sues particular to carbon blocks to enhance performance,
 whereas other types of filter media face different perfor-
 mance limitations.
      Indeed, the distinctions between carbon blocks and
 other types of filter media pervade the ’141 patent. For ex-
 ample, the specification explains that mixed or blended me-
 dia using carbon granules and other additives have limited
 contaminant removal capability. 

Id.

 at col. 3 l. 57–col. 4
 l. 11. This is because of the nature of loose granular media,
 namely, “particle size and packing geometry of the gran-
 ules,” which causes water to flow through the voids be-
 tween granules rather than directly contacting the
 granules. 

Id.

 at col. 3 l. 64–col. 4 l. 5. The ’141 patent ex-
 plains that one way to address the issue of water flowing
 through the voids is to use smaller granules, however, do-
 ing so comes at the cost of longer filtration time. 

Id.

 at col.
 4 ll. 20–24. Another factor affecting performance is that
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 BRITA LP v. ITC                                             11



 granular media is hydrophobic, meaning the granules tend
 to resist wetting and thus it is difficult for such a filter to
 readily absorb water. 

Id.

 at col. 4 ll. 41–67.
      Carbon blocks, by their nature, do not face the same
 problems and exhibit particular structural and chemical
 properties that make them advantageous for water filtra-
 tion. Because they are formed in “an integrated, porous,
 composite, carbon block,” 

id.

 at col. 13 ll. 23–24, there are
 no loose granules, and the carbon-block filter media can
 achieve more effective flow characteristics. 

Id.

 at col. 14
 l. 53–col. 15 l. 6. Also, “one can achieve a carbon block that
 is hydrophilic and readily absorbs water.” 

Id.

 at col. 14
 ll. 31–41.
      The ’141 patent purports to achieve further refine-
 ments of carbon-block filters by maximizing the surface
 area of the media available for filtration. 

Id.

 at col. 14
 ll. 39–41; see also 

id.

 at col. 17 ll. 39–42 (seeking to “max-
 imize the volume of a filtration media block media in a
 given cartridge or housing total volume, while decreasing
 pressure drop”). It also describes embodiments that em-
 ploy a multi-core structure for carbon blocks to ensure ef-
 fective water filtration. 

Id.

 at col. 23 ll. 18–45. The patent
 remarks on the “noteworthy” property of such carbon
 blocks as providing “excellent performance” for water fil-
 tration. 

Id.

 at col. 23 ll. 25–37. Thus, the specification it-
 self amply supports the conclusion that the ’141 patent only
 discloses carbon-block filters as being unique in their abil-
 ity to meet the claimed FRAP factor. The ’141 patent’s dis-
 closure does not demonstrate possession of non-carbon-
 block filter media achieving the claimed FRAP factor.
 Other evidence, discussed below, reinforces this conclusion.
      “[T]he level of detail required to satisfy the written de-
 scription requirement varies depending on the nature and
 scope of the claims and on the complexity and predictabil-
 ity of the relevant technology.” Ariad, 

598 F.3d at 1351

 (citing Capon v. Eshhar, 

418 F.3d 1349

, 1357–58 (Fed. Cir.
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 12                                             BRITA LP v. ITC




 2005)). The witness testimony in this case, while acknowl-
 edging that individual variables within the FRAP equation
 were known, demonstrates that achieving the required
 FRAP factor with any filter media was a complex task with
 unpredictable challenges. J.A. 23434–38 (respondents’ ex-
 pert, Dr. Gary Hatch, testifying to the interrelated nature
 of the variables in the FRAP equation, such that changing
 one variable in a filter can result in unpredictable changes
 in other variables and the ultimate FRAP value); see also
 J.A. 23467–68 (Dr. Hatch testifying that while it would be
 possible to configure a gravity-fed water filter in order to
 achieve “certain desired benefits, such as faster flow rate
 or improved contaminant reduction,” doing so would in-
 volve compromising other aspects of performance); J.A.
 22218–19 (Brita’s witness, Dr. Knipmeyer, testifying that
 the variables in the FRAP equation are “all interrelated”).
 This also comports with the statements of the applicant in
 the parent application to the ’141 patent that the art of
 making an effective filter is a “very difficult task” and that
 “small differences in many variables can make large differ-
 ences in . . . performance.” J.A. 41077, 41112–13.
      The inventors’ admissions that they did not create non-
 carbon-block filters achieving the claimed FRAP factor,
 and that doing so would involve “new technology” further
 confirms the conclusion that the ’141 patent’s disclosure
 does not demonstrate possession of non-carbon-block filter
 media achieving the claimed FRAP factor. See Commission
 Opinion, 

2023 WL 6290623

, at *22, *35–36. The inventor
 testimony here “illuminates the absence of critical descrip-
 tion in this case.” Nuvo Pharms. (Ir.) Designated Activity
 Co. v. Dr. Reddy’s Labs. Inc., 

923 F.3d 1368, 1381

 (Fed. Cir.
 2019). It is not enough for the patent to simply mention a
 desired outcome, i.e., “meeting the [FRAP] performance cri-
 teria,” ’141 patent col. 25 ll. 9–12, with non-carbon-block
 filter media. See Ariad, 

598 F.3d at 1357

. Here, the writ-
 ten description requirement demands that the specifica-
 tion provide more detail than merely listing examples of
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 BRITA LP v. ITC                                            13



 non-carbon-block filter media, particularly when the record
 evidence shows no such media met the claimed FRAP fac-
 tor at the time of invention.
     Brita offers three principal arguments for why the
 Commission erred in determining a lack of written descrip-
 tion. We find none of them persuasive, as they fail to over-
 come the express disclosures in the patent and undisputed
 testimony of the inventors and experts. First, Brita argues
 that the original claims provide sufficient written descrip-
 tion support. Appellant’s Br. 33–36. Second, Brita asserts
 that generic statements in the specification suggesting its
 invention is “applicable to all embodiments” provides con-
 structive reduction to practice. 

Id.

 at 36–38. Third, Brita
 argues that the ’141 patent adequately discloses repre-
 sentative examples and common structural features sup-
 porting its possession of the “genus” of filters covered by
 claim 1. 

Id.

 at 38–40. Brita recognizes that its arguments
 are “related,” id. at 33, and so we will address them to-
 gether.
      “[W]hile it is true that original claims are part of the
 original specification, that truism fails to address the ques-
 tion whether original claim language necessarily discloses
 the subject matter that it claims.” Ariad, 

598 F.3d at 1349

 (citation omitted); see also Enzo Biochem, Inc. v. Gen-Probe
 Inc., 

323 F.3d 956

, 968–69 (Fed. Cir. 2002) (“If a purported
 description of an invention does not meet the requirements
 of the statute, the fact that it appears as an original claim
 or in the specification does not save it.”). Brita’s original
 claims, reciting “filter media including at least activated
 carbon and a lead scavenger,” ’141 patent claim 1, do noth-
 ing to provide an adequate description of the types of filter
 media that can satisfy the claimed FRAP factor. Nor does
 the mere fact that these words appear in the specification
 suggest to a skilled artisan that the inventors were in pos-
 session of an invention comprising non-carbon-block filter
 media that can meet the claimed FRAP factor. None of the
 generic citations to different types of filter media, ’141
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 14                                              BRITA LP v. ITC




 patent col. 13 ll. 30–34, col. 25 ll. 5–12, and col. 26 ll. 30–
 37, relay any meaningful disclosure related to the specific
 FRAP factor limitations in the asserted claims beyond ex-
 pressing a desired result.
     We have held that a genus can be sufficiently disclosed
 by “either a representative number of species falling within
 the scope of the genus or structural features common to the
 members of the genus so that one of skill in the art can
 visualize or recognize the members of the genus.” Ariad,
 

598 F.3d at 1350

 (cleaned up). The problem with Brita’s
 genus argument, however, is that the ’141 patent does not
 identify a representative number of species or common
 structural features of members of the alleged genus. And
 the problem “is especially acute with genus claims that use
 functional language to define the boundaries of a claimed
 genus.” 

Id. at 1349

.
     Contrary to Brita’s argument that “the claimed inven-
 tion is a novel way of arranging known filter-media types,”
 Appellant’s Br. 39, claim 1 is defined functionally. The
 claim requires a functional result, namely, “achiev[ing]” a
 value of its self-defined FRAP factor of 350 or less. ’141
 patent col. 34 ll. 10–12. Indeed, the Commission recog-
 nized that the ’141 patent claims “any and all filtration me-
 dia types with activated carbon and a lead scavenger that
 meet the functional FRAP factor limitation.” Commission
 Opinion, 

2023 WL 6290623

, at *20. For a broad, functional
 claim to meet the written description requirement, the pa-
 tentee must demonstrate he “has invented species suffi-
 cient to support a claim to the functionally-defined genus.”
 Ariad, 

598 F.3d at 1349

.
     As discussed above, the ’141 patent does not disclose
 species other than carbon-block filters that can meet the
 claimed FRAP factor. Brita’s reliance on the specification’s
 statement that “[t]he nature of the filter meeting the fol-
 lowing performance criteria is independent of the exact em-
 bodiment of the filter,” is misplaced. Appellant’s Br. 35–36
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 BRITA LP v. ITC                                              15



 (citing ’141 patent col. 25 ll. 9–12). The specification does
 not demonstrate that satisfying the claimed FRAP factor
 can be decoupled from the properties of carbon-block fil-
 ters. Merely pronouncing that the “nature of the filter
 meeting” the FRAP factor is independent of the exact em-
 bodiment does not make it so, particularly in light of the
 patent’s testing results that demonstrate otherwise. And,
 while the specification may provide a listing of various
 types of filter media, including non-carbon-block media,
 and state that the FRAP factor criteria is “applicable” to
 filters using different types of media, id. at col. 13 ll. 30–34
 and col. 26 ll. 30–37, this does nothing to show possession
 of non-carbon-block media that meets the claim’s require-
 ments of a FRAP factor of 350 or less.
      Furthermore, the ’141 patent does not explain what
 common characteristics its carbon-block filters would share
 with non-carbon-block filters that might make them effec-
 tive for meeting the claimed FRAP factor. Instead, the pa-
 tent suggests the opposite, that “[t]he formulations of
 gravity fed carbon blocks disclosed are unique.” ’141 patent
 col. 26 ll. 63–65. As detailed above, the specification de-
 scribes numerous advantageous characteristics for water
 filtration that are unique to carbon blocks and which are
 inapplicable to other media, like loose granular and mixed
 media. The mere inclusion of activated carbon and lead
 scavenger is not enough to achieve the claimed FRAP fac-
 tor. Id. at Table 5 (showing mixed media filters, having
 activated carbon and lead scavenger, outside the claimed
 FRAP factor range). The ’141 patent’s failure to describe
 structural features common to the members of the genus
 “so that one of skill in the art can visualize or recognize the
 members of the genus” further demonstrates its lack of
 support for a claim to a genus encompassing non-carbon-
 block filters. Ariad, 

598 F.3d at 1350

 (cleaned up).
     Brita’s reliance on the knowledge of persons of ordinary
 skill is similarly unavailing. Brita alleges this case in-
 volves a “predictable art,” and so less detail is required to
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 16                                             BRITA LP v. ITC




 show adequate written description. Appellant’s Br. 33, 39.
 According to Brita, because other non-carbon-block filter
 media types were known to those of ordinary skill in the
 art, the ’141 patent’s detailed description of carbon-block
 embodiments “sufficed to show possession of an invention
 applicable to other well-known filter media types.” 

Id.

 at
 39–40. Brita also argues that a skilled artisan would know
 how to configure filters to achieve “certain desired bene-
 fits.” 

Id.

 at 39 (citing the questioning of Dr. Hatch). What
 Brita overlooks is that in the context of the FRAP equation
 (itself previously unknown), the ultimate effect of adjusting
 known variables was far from certain. That is, while one
 might know how to configure a filter to individually achieve
 “certain desired benefits,” such as “faster flow rate” or “im-
 proved contaminant reduction,” J.A. 23468, the effect that
 this has on the overall FRAP value is unpredictable due to
 the interrelatedness of variables. J.A. 23437. Even
 Dr. Knipmeyer admitted that the individual variables in
 the FRAP equation are “interrelated.” J.A. 22219. Thus,
 even accepting Brita’s argument that an ordinarily skilled
 artisan would know how to configure individual variables
 of the FRAP equation in other, well-known filter media, it
 does not follow that an ordinary artisan would know how
 to configure such filter media to achieve a FRAP factor of
 350 or less.
     “The knowledge of ordinary artisans may be used to in-
 form what is actually in the specification, but not to teach
 limitations that are not in the specification, even if those
 limitations would be rendered obvious by the disclosure in
 the specification.” Rivera, 

857 F.3d at 1322

 (cleaned up).
 Here, Brita cannot use the knowledge of a skilled artisan
 to make up for the specification’s lack of disclosure as to
 non-carbon-block filters that can meet the claimed FRAP
 factor. Brita has not shown that a skilled artisan would
 understand that the specification discloses non-carbon-
 block filters meeting the claimed FRAP factor.
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 BRITA LP v. ITC                                           17



     In sum, substantial evidence supports the Commis-
 sion’s determination that the asserted claims of the ’141
 patent lack adequate written description. The Commission
 appropriately found that the specification, read in light of
 the background knowledge in the art, failed to inform a
 skilled artisan that the inventors were in possession of fil-
 ter media other than carbon blocks that achieve the
 claimed FRAP factor.
                              II
      We separately address the Commission’s determina-
 tion that the asserted claims of the ’141 patent are non-
 enabled as to non-carbon-block filters. Section 112 sets
 forth the enablement requirement: “The specification shall
 contain a written description of the invention, and of the
 manner and process of making and using it, in such full,
 clear, concise, and exact terms as to enable any person
 skilled in the art to which it pertains . . . to make and use
 the same.” 

35 U.S.C. § 112

 ¶ 1 (pre-AIA). “If a patent
 claims an entire class of processes, machines, manufac-
 tures, or compositions of matter, the patent’s specification
 must enable a person skilled in the art to make and use the
 entire class. In other words, the specification must enable
 the full scope of the invention as defined by the claims.”
 Amgen Inc. v. Sanofi, 

598 U.S. 594

, 610 (2023). The stand-
 ard for enablement is whether a person skilled in the art
 can “make and use” the invention “without undue experi-
 mentation.” In re Wands, 

858 F.2d 731

, 735–37 (Fed. Cir.
 1988). Enablement is a question of law reviewed de novo
 based on underlying factual findings reviewed for substan-
 tial evidence. FS.com Inc. v. ITC, 

65 F.4th 1373, 1376

 (Fed.
 Cir. 2023).
     The Commission analyzed each of the Wands factors
 and concluded that it would take undue experimentation
 to make and use non-carbon-block filters that meet the
 claim requirements. Commission Opinion, 2023 WL
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 18                                               BRITA LP v. ITC




 6290623, at *36–37. Brita fails to identify any reversible
 error in the Commission’s analysis.
      Brita primarily argues that the Commission misread
 the specification by treating its admissions of the inability
 of tested mixed media filters to meet the claimed FRAP fac-
 tor as a failure by the inventors to apply their invention to
 non-carbon-block filter media. Oral Arg. at 1:37–2:21,
 (“The Commission’s decision hinges on a plain misreading
 of column 26.”). 1 We are not persuaded that the Commis-
 sion misinterpreted the specification of the ’141 patent.
      The relevant passage reads: “No mixed media filters
 tested met the claimed FRAP factor range due to their in-
 ability to remove particulate lead. The formulations of
 gravity fed carbon blocks disclosed are unique in [their]
 ability to meet the required FRAP factor.” ’141 patent
 col. 26 ll. 61–65. In its Wands factor analysis, the Commis-
 sion determined that the ’141 patent specification provides
 no teaching on how any filter other than carbon block can
 achieve the required FRAP factor. Commission Opinion,
 

2023 WL 6290623

, at *31–32. In support, the Commission
 cited this passage and others in the ’141 patent explaining
 that the tested mixed media filters “fail to adequately re-
 duce” lead concentrations. 

Id.

 at *31 (citing ’141 patent
 col. 31 ll. 9–10, col. 31 ll. 54–55). Despite the conceded fail-
 ures of the tested filters, the specification “does not provide
 a road map for how mixed media materials, or any type of
 filter other than carbon blocks, can achieve the required
 FRAP.” Commission Opinion, 

2023 WL 6290623

, at *31.
     Much of the same evidence discussed above with re-
 spect to written description also supports the Commission’s
 findings regarding enablement. For example, the ’141 pa-
 tent describes some of the specific problems that prevent



      1No. 24-1098, https://www.cafc.uscourts.gov/oral-
 arguments/24-1098_08052025.mp3.
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 BRITA LP v. ITC                                               19



 non-carbon-block filter media types, like mixed media,
 from achieving performance comparable to the carbon
 blocks that meet the claimed FRAP factor. See, e.g., ’141
 patent col. 3 ll. 51–67 (limited contaminant removal capa-
 bility), col. 4 ll. 41–67 (hydrophobic nature of granular me-
 dia). Even though the ’141 patent acknowledges that non-
 carbon-block filters are different from carbon-block filters,
 the ’141 patent provides no solutions to overcome the prob-
 lems associated with non-carbon-block filters, and instead
 characterizes its formulations of carbon-block filters meet-
 ing the claimed FRAP factor as “unique.” 

Id.

 at col. 26
 ll. 63–65. The inventors’ testimony confirms that the in-
 ventors did not create any working examples of non-car-
 bon-block filters, i.e., the inventors failed to create any
 filters besides carbon block that achieved the claimed
 FRAP factor. Commission Opinion, 

2023 WL 6290623

, at
 *31. Indeed, Dr. Knipmeyer testified that she “changed
 technology from a granular media to a carbon block” in de-
 veloping the invention. J.A. 32707–08.
      Brita further argues that the passage in column 26 of
 the patent is unremarkable because the mixed media fil-
 ters tested were prior art, which merely demonstrates nov-
 elty. Oral Arg. at 2:22–2:32. Regardless of whether the
 tested filters were prior art, the fact remains that the spec-
 ification does not provide any teaching or guidance on how
 to achieve the claimed FRAP factor with any type of filter
 besides carbon block, going so far as to disparage other fil-
 ter types. Taken together with the specification’s descrip-
 tion of “drawbacks,” “problems,” and “disadvantages” of
 non-carbon-block filter media, ’141 patent col. 3 l. 57–col. 4
 l. 24, the specification’s test results constitute a “clear[] and
 strong[] warn[ing]” against non-carbon-block filter media.
 See AK Steel Corp. v. Sollac, 

344 F.3d 1234, 1244

 (Fed. Cir.
 2003).
      Brita’s other principal argument is that the invention
 of the ’141 patent involves a “highly developed, predictable
 art.” Appellant’s Br. 30–32. This stands in stark contrast
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 20                                               BRITA LP v. ITC




 to the Commission’s findings on the Wands factors. Com-
 mission Opinion, 

2023 WL 6290623

, at *33–35. For exam-
 ple, the Commission, recognizing that the invention is
 “directed broadly to gravity-fed water filters that can
 achieve FRAP of less than 350,” found “the nature of the
 invention is not gravity-fed water filters generally, but
 gravity-fed water filters that achieve the claimed FRAP
 with any type of filter media,” 

id.

 at *33–34, and that the
 variables of the FRAP equation are “interrelated such that
 changing one variable will change other variables in a non-
 linear and unpredictable manner,” 

id. at *34

. We find no
 error in the Commission’s findings.
      Ample evidence in the record before us supports the
 finding of lack of predictability in the relevant field. At oral
 argument, Brita argued that both parties’ experts agreed
 that a skilled artisan would know how to modify the vari-
 ous components of a filter in order to achieve desired char-
 acteristics. Oral Arg. at 10:57–11:08 (citing to J.A.
 23467–68). However, as discussed in Section I of the dis-
 cussion section in this opinion concerning written descrip-
 tion, Brita’s argument fails to adequately account for the
 unpredictable nature of the FRAP equation itself due to the
 interrelatedness of its input characteristics. Respondents’
 expert, Dr. Hatch, merely acknowledged it was known that
 one could configure a filter to achieve “certain desired ben-
 efits” such as volume, flow rate, or contaminant reduction.
 J.A. 23468. That is, one could configure a filter to achieve
 a certain value for the input variables to the FRAP equa-
 tion. It does not follow, however, that one could configure
 a filter of any media type to achieve the claimed FRAP fac-
 tor—let alone that the specification enabled an ordinary ar-
 tisan to do so without undue experimentation. Dr. Hatch
 testified that the input variables to the FRAP equation are
 “interrelated” and that “when you change one of these fac-
 tors, you do not know what is going to be the final result of
 your FRAP value.” J.A. 23437. Dr. Knipmeyer also
 acknowledged that the variables are “interrelated.” J.A.
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 BRITA LP v. ITC                                            21



 22218–19. Moreover, the testimony of Brita’s expert, Dr.
 Benny Freeman, demonstrates agreement with this princi-
 ple that a particular change to one variable in the FRAP
 equation affects others. The ’141 patent itself recognizes
 the tradeoff relationship between some aspects of filter
 characteristics in the context of granular media. ’141 pa-
 tent col. 4 ll. 41–67 (the goal of fast flowrate is counter to
 long lifetime and effective contaminant removal). But im-
 portantly, the patent does not explain how to adjust the
 various characteristics to achieve the claimed FRAP factor
 for such granular media, or for any filter media besides car-
 bon block.
     Furthermore, Dr. Knipmeyer’s testimony that creating
 non-carbon-block embodiments would involve “new tech-
 nology,” J.A. 32984, severely undercuts Brita’s reliance on
 the level of skill in the art. The Commission found that
 “how to develop that new technology remains unclear and
 unpredictable from [the] patent disclosure.” Commission
 Opinion, 

2023 WL 6290623

, at *35. As discussed above,
 the specification lacks any guidance on how to achieve the
 claimed FRAP factor with filter media other than carbon
 block.
     We have held that “[i]t is the specification, not the
 knowledge of one skilled in the art, that must supply the
 novel aspects of an invention in order to constitute ade-
 quate enablement.” Genentech, Inc. v. Novo Nordisk A/S,
 

108 F.3d 1361, 1366

 (Fed. Cir. 1997). Brita’s reliance on
 Dr. Freeman’s testimony that one could use the same
 “starting materials” and reach the claimed invention es-
 sentially places the entire inventive effort on one of ordi-
 nary skill in the art. This violates the very quid pro quo
 central to the enablement requirement—“requiring a pa-
 tentee to teach the public how ‘to practice the full scope of
 the claimed invention.’” McRO, Inc. v. Bandai Namco
 Games Am. Inc., 

959 F.3d 1091

, 1091–1100 (Fed. Cir. 2020)
 (quoting AK Steel, 

344 F.3d at 1244

). In light of other rec-
 ord evidence demonstrating the differences between carbon
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 22                                             BRITA LP v. ITC




 blocks and other filter media types, the specification’s lack
 of disclosure to guide one of ordinary skill to achieve the
 claimed FRAP factor with other filter media is fatal to
 Brita’s argument.
     We conclude that substantial evidence supports the
 factual findings as to the Wands factors underlying the
 Commission’s enablement determination. The record thus
 supports the Commission’s legal conclusion that the ’141
 patent required undue experimentation to enable the full
 scope of the asserted claims.
                              III
     The Commission ultimately determined there could be
 no section 337 violation because the asserted claims of the
 ’141 patent were invalid. We are not required to address
 every possible ground on which the Commission’s determi-
 nation might be sustained. Solomon Techs., Inc. v. ITC,
 

524 F.3d 1310, 1320

 (Fed. Cir. 2008). Therefore, we decline
 to reach the issue of indefiniteness.
                         CONCLUSION
      For the foregoing reasons, we affirm.
                        AFFIRMED