Dataproducts DPC51ANTWN Remanufactured Ink Cartridge Replacement for HP #21 (Twin Pack - Black) Assembled in USA Premium ink cartridges that meet or exceed OEM quality, page yield, and reliability 1-year warranty, 100% satisfaction guarantee Compatible Hardware: HP DeskJet 3910, 3915, 3918, 3920, 3930, 3938, 3940, D1311, D1320, D1330, D1341, D1360, D1368...; Deskjet All-In-One F310, F325, F335, F350, F370,...; FAX 1250, 3180; OfficeJet 4311, 4312, 4314, 4315, 4315v...; PSC 1401, 1402, 1403... Twin Pack