Reman.
15 (C6615A) Black Cartridge compatible with:
DeskJet 3810, 3816, 3820, 3822, 810c, 812c, 825, 840c, 841c, 842c, 843c, 845, 920c, 940, 310, Fax 1230
OfficeJet 5110, v30, v40, v45, PSC 500, 720, 75
The use of compatible supplies does not void your printer warranty.