The genuine Lexmark 56F2U00 is part of the industry leaders unique Return Programme that reduces the cost of purchasing this black toner cartridge. By purchasing this eco-friendly toner you agree to return the cartridge (for free) to be recycled afterwards. As a ultra high capacity original Lexmark toner cartridge, the 56F2U00 has a significantly lower cost per page than other capacity units that are also available for your mono laser printer.This original Lexmark 56F2U00 black toner cartridge has an estimated page yield of 25,000 prints. Once compatible machines (like the Lexmark MS521dn) believe the 56F2U00 toner cartridge is empty, the unit will cease to function, allowing you to take advantage of the free recycling scheme mentioned previously.