Twin pack includes No. 28 Black Return Program Cartridge and No. 29 color Return Program Cartridge. These cartridges are nonrefillable cartridges licensed for single use only. Return empty cartridge only to Lexmark for remanufacturing, refilling or recycling. Cartridges are designed for use with the Lexmark X2500, X2510, X2530, X2550, X5070, X5075, X5320, X5340, X5410, X5495, Z845, Z1300, Z1310 and Z1320.