X644e, X646e Extra High Yield Return Program Print Cartridge (32K) Lexmark 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 reuse or recycling. The Lexmark X644e and X646e MFP print cartridges are designed for easy installation and quality performance to keep printers productive under heavier usage demands and to even further diminish per page costs. The X644e and X646e MFP Extra High Yield Print Cartridge is not compatible with other Lexmark MFPs or printers.