Premium 51625A (HP 25) Tri-Color Inkjet Cartridge fully compatible with the HP C2121A, DeskJet 200, 310, 311, 320, 340, 400, 420, 500, 520, 540, 550c, 560, Portable, DeskWriter 310, 320, 340, 400, 500c, 510, 520, 540, 550, 560, C Also fits Encad, Novajet, Xerox, Apollo, and Summagraphics. The use of compatible supplies does not void your printer warranty.