HP DeskJet 550C

HP (HP 25) 51625A Remanufactured Tri-Color Inkjet Cartridge
51625A Tri-Color Inkjet Cartridge 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.

HP 51626A (HP 26) Black Inkjet Cartridge
51626A Black Inkjet Cartridge compatible with the HP 2276a/ 2277a/ 2279a DeskWriter/ C2121A/ C2124A/ DesignJet 200/ 220/ 600/ DeskJet 200cci/ 400/ 420/ 500/ 505k/ 510/ 520/ 540/ 550c/ 560c/ DeskJet Plus/ DeskWriter 400 Also fits Agfa/ Apollo/ Apple/ Citizen/ Daewoo/ DEC/ Encad/ Olivetti/ Olympia/ Panasonic/ Pitney Bowes/ Sharp/ Siemens/ Stielow/ Triumph Adler/ and many other. The use of compatible supplies does not void your printer warranty.