High-quality, Return Program imaging unit is essential to Lexmark Print System Performance in Lexmark printers including the following series, MX710, MX810, MX811, MX812, MS710, MS711, MS810, MS811 and MS812. 520Z imaging unit is designed to work best with Unison toner to perform in an innovative, shake-free print system. Enables full use of toner without shaking the cartridge. Unison toner technology for high-quality printing and device reliability.