  United States Court of Appeals
      for the Federal Circuit
                 ______________________

       ARKEMA INC. AND ARKEMA FRANCE,
              Plaintiffs-Appellants,

                            v.

       HONEYWELL INTERNATIONAL, INC.,
              Defendant-Appellee.
            ______________________

                       2012-1308
                 ______________________

   Appeal from the United States District Court for the
Eastern District of Pennsylvania (Philadelphia) in No. 10-
CV-2886, Judge William H. Yohn, Jr.
                 ______________________

               Decided: February 5, 2013
                ______________________

     John DiMatteo, Willkie Farr & Gallagher, LLP, of
New York, New York, argued for plaintiffs-appellants.
With him on the brief were Michael W. Johnson and
Aparnaa B. Saini.

       Gregg F. LoCascio, Kirkland & Ellis, LLP, of Wash-
ington, DC, argued for defendant-appellee. With him on
the brief were Sean M. McEldowney and Anders P. Fjell-
stedt; and Laura M. Burson, Kirkland & Ellis, LLP, of Los
Angeles, California.
                 ______________________
2            ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.


    Before DYK, PLAGER, and O'MALLEY, Circuit Judges.
DYK, Circuit Judge.
    Defendant Honeywell International, Inc. (“Honey-
well”) and plaintiffs Arkema Inc. and Arkema France
(“Arkema”) compete in the manufacture and sale of auto-
motive refrigerants.     Honeywell owns United States
Patent No. 8,033,120 (“the ’120 patent”) and United
States Patent No. 8,065,882 (“the ’882 patent”). Arkema
sought a declaratory judgment that by entering into
contracts to supply HFO-1234yf (“1234yf”), a next-
generation automotive refrigerant, to automobile manu-
facturers for use in automobile air conditioning systems,
it would not incur liability as an indirect infringer under
the ’120 and ’882 patents, which cover methods of using
1234yf in automobile air conditioning systems.
    The district court refused to entertain Arkema’s re-
quest for declaratory judgment, denying Arkema’s motion
to supplement its complaint to add declaratory claims
with respect to the ’120 and ’882 patents on the grounds
that there was no justiciable controversy.
    We find that the district court erred in its determina-
tion that there is no justiciable controversy, and reverse
the district court’s denial of Arkema’s motion to supple-
ment. We remand for further proceedings consistent with
this opinion.
                      BACKGROUND
    Before the mid-2000s, automobile manufacturers used
a refrigerant called R-134a for automobile air condition-
ers. In 2006, global warming concerns prompted the
European Union to enact new regulations requiring
automobiles to use refrigerants with low “global warming
potential.” The regulations apply to all new automobile
platforms beginning in 2013 and to all new automobiles
by 2017. The United States has not yet adopted similar
 ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.           3
regulations, but U.S. and foreign automobile manufactur-
ers are both transitioning to 1234yf, which has a low
global warming potential, and has become “remarkably
successful,” according to Honeywell’s expert, Thomas R.
Varner. 1 J.A. 376. Automobile manufacturers are al-
ready signing long-term contracts to purchase 1234yf.
Both Arkema and Honeywell wish to supply the industry
with 1234yf, and both have invested substantial resources
in the production of 1234yf. Arkema has already built a
manufacturing facility for 1234yf in France and has plans
to build another facility to meet growing demand. Hon-
eywell has a plant in New York and is developing a much
larger facility in Louisiana. Arkema is concerned that if it
enters into supply contracts it will indirectly infringe
Honeywell’s patents.
    Honeywell owns a number of patents relating to
1234yf. United States Patent No. 7,534,366 (“the ’366
patent”) claims a heat transfer composition combining
1234yf with a polyalkylene glycol lubricant. Claim 1
reads:
   1. A heat transfer composition for use in an air
   conditioning system comprising:
       (a) at least about 50% by weight of [1234yf]
       having no substantial acute toxicity; and

   1     Although there are other refrigerants with low
global warming potential, Arkema alleges that 1234yf
“has become the de facto standard refrigerant in Europe
and the United States.” First Supp. Compl. 2, Arkema,
Inc. v. Honeywell Int’l, Inc., No. 10-CV-2886 (E.D. Pa. Dec.
15, 2011), ECF No. 58-1. There is no dispute that there is
substantial demand for 1234yf. Varner testified that
“[t]here is extensive evidence of demand for [1234yf]
among automobile manufacturers,” and that “[t]his de-
mand exists even though there is currently no regulatory
requirement mandating its use.” J.A. 370-71.
4                ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.
           (b) at least one poly alkylene glycol lubricant
           in the form of a homopolymer or co-polymer
           consisting of 2 or more oxypropylene groups
           and having a viscosity of from about 10 to
           about 200 centistokes at about 37° C.
’366 patent col. 13 ll. 37-45. Polyalkylene glycol lubri-
cants are part of the heat transfer composition in almost
all automobile air conditioning systems. Similarly, Unit-
ed States Patent No. 7,279,451 (“the ’451 patent”) claims
a heat transfer composition including 1234yf with a
sufficiently low global warming potential. 2 ’451 patent
col. 17 l. 57 to col. 18 l. 8.
    Most pertinent here, Honeywell also owns U.S. pa-
tents directed to methods of using 1234yf. The ’120
patent, which claims priority to the ’366 patent, is di-
rected to a method of cooling air using 1234yf combined
with a lubricant. 3 Claim 1, which is representative,
reads:
        1. A method of cooling air comprising:
           (a) providing a heat transfer fluid comprising
           at least one lubricant and [1234yf]; and
           (b) cooling said air by vaporizing said refriger-
           ant by causing heat to be transferred from the
           air being cooled to said heat transfer fluid.



    2   Some claims of the ’451, ’120, and ’882 patents are
not limited to 1234yf; they include claim limitations
directed to genuses of compounds of which 1234yf is a
member. Because only 1234yf is at issue in this appeal,
we refer to such broader claims as being directed to
1234yf even though they are not limited to it.
   3    The ’120 patent is currently the subject of an inter
partes reexamination proceeding initiated by a third
party.
 ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.           5
’120 patent col. 13 ll. 14-34. Similarly, the ’882 patent
claims priority to the ’451 and ’366 patents, and covers
methods of cooling air in an automobile with 1234yf.
Claim 1 reads:
   1. A method of transferring heat to or from a flu-
   id or body to provide cooling of air in an automo-
   bile, said method comprising:
       (a) providing a heat transfer system compris-
       ing an automobile air conditioning system;
       (b) providing in said system a heat transfer
       composition comprising at least one lubricant
       and [1234yf].
’882 patent col. 17 ll. 33-56. Honeywell also owns Euro-
pean Patent No. 1,716,216, which is a counterpart to
Honeywell’s U.S. patents on 1234yf and includes method
claims.
    In November 2009, Honeywell filed suit against
Arkema for infringement of the European patent based on
Arkema’s offers to sell 1234yf in Germany. In June 2010,
Arkema brought suit against Honeywell in the United
States District Court for the Eastern District of Pennsyl-
vania, seeking declaratory judgment that the ’451 and
’366 composition patents were invalid and not infringed
by Arkema’s plans to supply U.S. automobile manufactur-
ers with 1234yf. 4 Honeywell counterclaimed, asserting

   4    During this litigation and prior to this appeal, the
United States Patent and Trademark Office rejected all
claims of the ’451 patent during an inter partes reexami-
nation proceeding. Honeywell then gave Arkema a cove-
nant not to sue on the ’451 patent, and the district court
dismissed both parties’ claims directed to the ’451 patent.
The ’366 patent remains a part of the litigation before the
district court, which was stayed pending disposition of
this appeal.
6             ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.
that Arkema’s sale and offer for sale of 1234yf in the
United States constituted infringement of both patents.
Honeywell specifically alleged (and Arkema admitted)
that Arkema “has sought, and continues to seek, to com-
pete with Honeywell for supplying 1234yf to automobile
manufacturers in the U.S.,” and that Arkema is “aware
that U.S. automobile manufacturers purchase . . . 1234yf
primarily or exclusively for use in automobile air condi-
tioning systems.” Def.’s Answer, Affirmative Defenses
and Countercls. at 15, Arkema, Inc. v. Honeywell Int’l,
Inc., No. 10-CV-2886, (E.D. Pa. Aug. 20, 2010), ECF No.
10 (“Honeywell Answer”). While the suit was in discov-
ery, Honeywell obtained the ’120 and ’882 patents.
Arkema then moved to supplement its complaint to seek
declaratory judgment of non-infringement and invalidity
as to the ’120 and ’882 patents, fearing liability under
those patents should it proceed with plans to sell 1234yf
to U.S. automobile manufacturers.
     On February 3, 2012, the district court denied
Arkema’s motion to supplement. Arkema, Inc. v. Honey-
well Int’l, Inc., No. 10-CV-2886, 2012 WL 360189, at *1
(E.D. Pa. Feb. 3, 2012). Although the district court found
that there would be no undue prejudice to Honeywell if
Arkema were permitted to supplement its complaint, the
district court found that Arkema’s new claims did not
present an Article III case or controversy. Id. at *2 n.5.
As a result, the district court concluded that those claims
could not survive a motion to dismiss and that supple-
mentation would therefore be futile. Id. at *3. The dis-
trict court concluded that Arkema could not be charged
with directly infringing the ’120 and ’882 patents because,
as a mere supplier, Arkema had no plans to use 1234yf in
any manner that could directly infringe those patents,
which cover only methods of using 1234yf. Id. at *4. As
for indirect infringement, the district court concluded that
Arkema “is not currently or imminently in danger of
 ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.              7
facing liability for contributory infringement or induced
infringement.” Id. at *5.
    On March 8, 2012, with the agreement of both parties,
the district court certified its order denying Arkema’s
motion to supplement as a final judgment appealable
under Fed. R. Civ. P. 54(b). Order, Arkema, Inc. v. Hon-
eywell Int’l, Inc., No. 10-CV-2886 (E.D. Pa. Mar. 8, 2012),
ECF No. 80. Arkema timely appealed. We have jurisdic-
tion under 28 U.S.C. § 1295(a)(1).
                         DISCUSSION
    The district court’s denial of Arkema’s motion to sup-
plement its complaint was based on its conclusion that
Arkema’s supplemental claims were not justiciable. We
review that legal conclusion de novo. Teva Pharms. USA,
Inc. v. Novartis Pharms. Corp., 482 F.3d 1330, 1335-36
(Fed. Cir. 2007). Arkema bears the burden of proving the
existence of an Article III case or controversy. See Arris
Grp., Inc. v. British Telecommc’ns PLC, 639 F.3d 1368,
1373 (Fed. Cir. 2011).
                              I
    The Declaratory Judgment Act provides that “[i]n a
case of actual controversy within its jurisdiction, . . . any
court of the United States, upon the filing of an appropri-
ate pleading, may declare the rights and other legal
relations of any interested party seeking such declaration,
whether or not further relief is or could be sought.” 28
U.S.C. § 2201(a). In authorizing this procedure, Congress
recognized that declaratory judgment is “especially useful
in avoiding the necessity . . . of having to act at one’s peril
or to act on one’s own interpretation of his rights, or
abandon one’s rights because of a fear of incurring dam-
ages.” S. Rep. No. 73-1005, at 2-3 (1934). Thus, the
Supreme Court has held that Article III does not require
that a landowner “bet the farm” by risking forfeiture of
his land before challenging the constitutionality of a state
8             ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.
anti-alien land law. See Terrace v. Thompson, 263 U.S.
197, 216 (1923). Nor does Article III require an individual
to risk prosecution under state criminal trespass laws
before seeking declaratory judgment of his rights. Steffel
v. Thompson, 415 U.S. 452, 454 & n.1, 459 (1974).
    The Supreme Court’s most pertinent decision is
MedImmune, Inc. v. Genentech, Inc., 549 U.S. 118 (2007).
There, the Court held that Article III did not require a
patent licensee to cease payment under the license in
order to seek declaratory judgment of the patent’s invalid-
ity. Id. at 128, 137. The Court reiterated that the proper
test of when an action for declaratory judgment presents a
justiciable controversy is “whether the facts alleged,
under all the circumstances, show that there is a substan-
tial controversy, between parties having adverse legal
interests, of sufficient immediacy and reality to warrant
the issuance of a declaratory judgment.” Id. at 127 (quot-
ing Md. Cas. Co. v. Pac. Coal & Oil Co., 312 U.S. 270, 273
(1941)). The Court also made clear that this test is satis-
fied when the declaratory judgment plaintiff is put “to the
choice between abandoning his rights or risking prosecu-
tion.” Id. at 129. Thus, the Court held that “[t]he rule
that a plaintiff must destroy a large building, bet the
farm, or . . . risk treble damages . . . before seeking a
declaration of its actively contested legal rights finds no
support in Article III.” Id. at 134. In other words, a
declaratory judgment is “an alternative to pursuit of the
arguably illegal activity.” Id. at 129 (quoting Steffel, 415
U.S. at 480 (Rehnquist, J., concurring)).        Following
MedImmune, we have held that “Article III jurisdiction
may be met where the patentee takes a position that puts
the declaratory judgment plaintiff in the position of either
pursuing arguably illegal behavior or abandoning that
which he claims a right to do.” SanDisk Corp. v.
STMicroelectronics, Inc., 480 F.3d 1372, 1381 (Fed. Cir.
2007).
 ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.            9
                             II
    On its face, this is a quintessential example of a situa-
tion in which declaratory relief is warranted. The rele-
vant facts are not in dispute. Arkema has concrete plans
for offering 1234yf to automobile manufacturers for use in
automobile air conditioning systems and now desires to
enter into contracts with automobile manufacturers to
supply 1234yf. However, if Honeywell’s view of its patent
coverage prevails, then proceeding with its plans would
expose Arkema to significant liability. Indeed, Honeywell
has made it clear that it will protect its patent rights
against any such activity by Arkema. Honeywell has
already asserted claims against Arkema in the United
States for infringement of other patents covering the
same technology and in Germany relating to Arkema’s
activities involving 1234yf and automobile air condition-
ing systems. There is far more here than a mere showing
of “economic injury.” Rather, Arkema is seeking a deter-
mination of a legal right under the method patents cover-
ing its own activities. There is a controversy between
Arkema and Honeywell as to legal rights in the 1234yf
technology.
                             III
    The district court nevertheless concluded that there
was no justiciable controversy. We disagree. First, the
district court determined that “Arkema has neither al-
leged nor offered evidence that an Arkema customer has
committed an act of direct infringement,” relying on our
decision in Arris. Arkema, 2012 WL 360189, at *5. To the
extent that the district court suggests that there must
actually be acts of direct infringement the district court is
mistaken. While Arris found such accusations sufficient
for declaratory judgment jurisdiction in a suit brought by
a supplier, Arris did not set forth an overarching test for a
supplier’s standing to seek a declaratory judgment re-
garding its potential indirect infringement liability;
10             ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.
rather, it identified circumstances that have been held
sufficient (rather than necessary) for declaratory judg-
ment jurisdiction. 639 F.3d at 1375. Nor is it necessary
that a patent holder make specific accusations against
either the potential direct infringers or Arkema. Id. at
1379; ABB Inc. v. Cooper Indus., LLC, 635 F.3d 1345,
1348 (Fed. Cir. 2011) (“A specific threat of infringement
litigation by the patentee is not required to establish
jurisdiction.”).
    Even the district court appeared to agree that actual
direct infringement is not required. The court concluded
that:
     While specific infringing acts are not necessary for
     declaratory-judgment jurisdiction where there is
     specific planned activity, Arkema has not shown
     that its specific planned activity (supplying
     [1234yf]) may subject it to liability for indirect in-
     fringement. Arkema has not adduced any evi-
     dence as to which potential customer will
     imminently commit an act of direct infringement,
     when this may happen, or how.
Arkema, 2012 WL 360189, at *6 (citation omitted). The
level of specificity required by the district court does not
comport with our cases. There is no question that auto-
mobile manufacturers install air conditioners in the
automobiles that they sell, that they test those air condi-
tioners, and that the purchasers of those automobiles use
the air conditioners. It is also undisputed that Arkema
wishes to sell (and that manufacturers wish to purchase)
1234yf for use in those air conditioners, and that Honey-
well’s position is that use of 1234yf in automobile air
conditioners infringes the method patents. There is thus
no question that both the automobile manufacturers and
their ultimate consumers will—in Honeywell’s view—
infringe the method patents. There is no requirement
that Arkema identify the particular manufacturers that
 ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.           11
will purchase the 1234yf or the particular automobile
purchasers who will purchase the cars from the manufac-
turers, or the particular dates on which this will occur.
     Nor is it necessary that Honeywell have directly ac-
cused Arkema of potential indirect infringement. Even
under the now-discarded reasonable apprehension of suit
test, 5 it was well established that a sufficient controversy
existed for declaratory judgment jurisdiction where the
patentee had accused the declaratory judgment plaintiff
of misappropriating the same technology in related litiga-
tion. Goodyear Tire & Rubber Co. v. Releasomers, Inc.,
824 F.2d 953, 955 (Fed. Cir. 1987) (patents issued during
trade secret litigation regarding the same technology); see
also Vanguard Research, Inc. v. PEAT, Inc., 304 F.3d
1249, 1255 (Fed. Cir. 2002); Teva, 482 F.3d at 1344-45
(“Related litigation involving the same technology and the
same parties is relevant in determining whether a justici-
able declaratory judgment controversy exists on other
related patents.”). Here, Honeywell has accused Arkema
of infringing its rights with respect to 1234yf in litigation
over the closely related ’366 patent and the European
patent claiming methods of using 1234yf. This creates a
sufficient affirmative act on the part of the patentee for
declaratory judgment purposes. Furthermore, Honeywell
has declined to grant Arkema a covenant not to sue on the
’120 and ’882 patents, which further suggests that there is
an active and substantial controversy between the parties
regarding their legal rights with respect to those patents.
Arris, 639 F.3d at 1381; see also Already, LLC v. Nike,
Inc., 568 U.S. ___ (2013) (slip op. at 5-6) (covenant not to

    5   While a declaratory judgment plaintiff is no long-
er required to demonstrate a reasonable apprehension of
suit, MedImmune, 549 U.S. at 132 n.11; SanDisk, 480
F.3d at 1380, such a showing remains sufficient to estab-
lish jurisdiction. Streck, Inc. v. Research & Diagnostic
Sys., Inc., 665 F.3d 1269, 1282 (Fed. Cir. 2012).
12            ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.
sue was sufficient to moot Article III controversy because
it broadly barred trademark infringement claim against
the declaratory judgment plaintiff, its distributors, and its
customers).
     Second, the district court found that Arkema did not
allege an adequate “specific planned activity” because
“there are methods for using [1234yf] in an automobile
air-conditioning system that will not infringe the method
patents.” Arkema, 2012 WL 360189, at *6. On their face
the method patents cover any use of 1234yf in an automo-
bile air conditioner as part of a heat transfer composition
(i.e., combined with a lubricant). See ’120 patent col. 13 ll.
14-34; ’882 patent col. 19 ll. 42-62. And at oral argument,
Honeywell conceded that some claims of the ’120 and ’882
patents do not require a specific lubricant and that all
known uses of 1234yf in an automobile air conditioning
system require a lubricant. Thus, Honeywell admits that
there are no known methods of using 1234yf in an auto-
mobile air conditioning system that do not at least argua-
bly infringe its patents. 6
    In response to Arkema’s interrogatories, Honeywell
asserted that “Arkema knew that []1234yf was especially


     6  There is also no dispute that Arkema’s prospective
customers will likely use 1234yf with a polyalkylene
glycol lubricant, as some claims require. Honeywell
specifically alleged that Arkema’s customers would “pur-
chase 1234yf primarily or exclusively for use with certain
lubricants,” Honeywell Answer 16, and its expert testified
that “Polyalkylene Glycol[] is the type of lubricant that is
generally used in belt-driven automobile air conditioning
systems.” J.A. 292. Likewise, Arkema states that “auto-
mobile manufacturers will use polyalkylene glycol, the
standard lubricant in the industry, in, at least, the vast
majority of their air conditioning systems.” Appellant’s
Br. 25.
 ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.          13
made for use in air conditioning systems . . . and that non-
infringing uses of [1234yf] . . . if any, were experimental
and/or not substantial.” J.A. 268. Similarly, Honeywell’s
expert, Donald B. Bivens, testified that 1234yf “is not a
common component suitable for substantial non-
infringing uses.” J.A. 320. And while a party need not
concede infringement to demonstrate a justiciable contro-
versy, see Arrowhead Indus. Water, Inc. v. Ecolochem,
Inc., 846 F.2d 731, 738 (Fed. Cir. 1988), Arkema admits
that “there are no non-infringing uses for 1234yf as a
refrigerant in automobile air-conditioning systems” and
that “any design employing 1234yf in an automobile will
infringe the broad claims of the new patents.” Appellant’s
Br. 33. So too there can hardly be any question that
Arkema would arguably be liable for induced infringe-
ment if it sells 1234yf for use in automobile air condition-
ing systems. Where, as here, there is no dispute that the
intended use would be at least arguably infringing and
actively encouraged by the declaratory judgment plaintiff,
a controversy is “sufficiently real” for the purposes of
declaratory judgment jurisdiction.
    Third, the district court found that any “threshold
acts of direct infringement are not sufficiently immediate
to create a justiciable controversy” because “the first
predicted commercial launch of any product using
[1234yf] is at least one year away.” Arkema, 2012 WL
360189, at *6. Honeywell does not dispute that long-term
supply contracts are already being signed. Indeed, Hon-
eywell’s expert Thomas R. Varner testified that Honey-
well and other suppliers of 1234yf have already entered
into numerous long-term contracts to supply 1234yf to
automobile manufacturers. Such circumstances have put
Arkema in a present position of either committing to
contracts that could expose it to liability for indirect
infringement or abandoning its plans to supply 1234yf to
automobile manufacturers in the United States. There-
fore, Arkema’s need for a declaratory judgment clarifying
14            ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.
its rights is sufficiently immediate under Article III. See
MedImmune, 549 U.S. at 134.
    This is not a case where the declaratory judgment
plaintiff alleged only that it would “consider” potentially
infringing activities. 7 Rather, Arkema alleges a present
intent to supply automobile manufacturers in the United
States with 1234yf for potentially infringing uses. Nor is
this a case where “the accused infringers had not distrib-
uted sales literature [or] prepared to solicit orders.” Lang
v. Pac. Marine & Supply Co., 895 F.2d 761, 765 (Fed. Cir.
1990). Honeywell’s own allegations state that Arkema is
marketing 1234yf to automobile manufacturers in the
United States, and Arkema admits that it has already
responded to at least one supply request from a U.S.
automobile manufacturer and that it is “poised to respond
to other requests for quotations to supply 1234yf.” First
Supp. Compl. 7, Arkema, Inc. v. Honeywell Int’l, Inc., No.
10-CV-2886 (E.D. Pa. Dec. 15, 2011), ECF No. 58-1.
     Finally, the district court concluded that Arkema had
not satisfied the “‘reality’ requirement” under MedIm-
mune because it “has not demonstrated that the design of
its customers’ products . . . is sufficiently fixed.” Arkema,
2012 WL 360189, at *6. As discussed above, however,
Arkema’s relevant plans are clear. It intends to offer
1234yf for use in automobile air conditioning systems.
Honeywell’s expert Dr. Varner testified that “[b]oth

     7  E.g., Ass’n of Molecular Pathology v. U.S. Patent
& Trademark Office, 689 F.3d 1303, 1321 (Fed. Cir. 2012)
(holding that doctors who alleged only that they would
“consider” resuming potentially infringing activities
lacked standing to seek a declaratory judgment); Benitec
Austl., Ltd. v. Nucleonics, Inc., 495 F.3d 1340, 1346 (Fed.
Cir. 2008) (finding that the declaratory judgment plaintiff
lacked standing because it admitted that it did not antici-
pate pursuing infringing activity for several years, “if
ever”).
 ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.         15
Arkema and Honeywell provided quotes to supply
[1234yf] to automobile manufacturers for use as the
refrigerant component of heat transfer compositions for
automobile air conditioning systems.” J.A. 376 (emphasis
added). Dr. Varner also repeatedly emphasized the “high
demand for [1234yf] in heat transfer compositions in air
conditioning systems.” J.A. 381 (emphasis added). This is
not a situation in which there is uncertainty about
whether the supplier’s product is going to be used in a
way that might or might not infringe the patentee’s
rights. 8 Rather, the contentions of both parties make
clear that Arkema’s prospective customers plan to use
1234yf with a lubricant in automobile air conditioning
systems. Any uncertainty concerning the precise parame-
ters under which automobile manufacturers will use
1234yf is irrelevant because Honeywell’s patents are not
limited to a particular set of parameters.
    Accordingly, we conclude that the controversy be-
tween Arkema and Honeywell regarding the ’120 and ’882
patents is “of sufficient immediacy and reality to warrant
the issuance of a declaratory judgment.” MedImmune,
549 U.S. at 127.
                        CONCLUSION
    We hold that the district court erred in denying
Arkema leave to supplement its complaint by adding
declaratory judgment claims regarding the ’120 and ’882
patents. There is an Article III case or controversy be-
tween Arkema and Honeywell regarding the infringement

   8    E.g., Matthews Int’l Corp. v. Biosafe Eng’g, LLC,
695 F.3d 1322, 1330-31 (Fed. Cir. 2012) (declaratory
judgment plaintiff’s claim lacked sufficient reality when
the equipment it sold could be operated using either
infringing or non-infringing parameters, and the plaintiff
did not allege that the equipment would be operated using
infringing parameters).
16            ARKEMA INC.   v. HONEYWELL INTERNATIONAL INC.
and validity of those patents. We reverse the district
court’s denial of Arkema’s motion to supplement its
complaint, and remand for further proceedings consistent
with this opinion.
             REVERSED and REMANDED
     Costs to Arkema.
