Return Program toner cartridge features the Unison Toner's unique formulation that consistently delivers outstanding image quality, ensures long-life print system reliability and promotes superior sustainability - all in an innovative, shake-free print system. Genuine Lexmark toner is engineered to work best together with your Lexmark printer, delivering excellent print quality from the first page to the last in Lexmark MS321dn, MS421dn, MS421dw, MS521dn, MS521dn, MS621dn, MS622de, MX321adn, MX321adw, MX421ade, MX521de, MX521ade, MX522adhe, MX622ade and MX622adhe. Lexmark Return Program cartridges are patented print cartridges sold at a discount in exchange for the customer's agreement to the license requirement that the cartridges will be used only once and returned only to Lexmark for remanufacturing or recycling. Cartridges are licensed for single use only and will stop working after delivering a fixed amount. Standard-yield cartridge yields approximately 6,000 standard pages.