Return Program print cartridges are designed for use with Lexmark All-in-One Machines X3530, X3550, X4530 and X4550. The No. 23 ink cartridge yields approximately 215 pages while the No. 24 ink cartridge yields approximately 185 pages. Return Program cartridges are sold at a discount, versus the prices of regular cartridges, in exchange for the customer's agreement to use the cartridge only once and return it only to Lexmark for remanufacturing or recycling.