You simply cannot operate a Lexmark laser printer without a functioning drum unit - like the 500Z crum unit - being installed. With a page yield that far exceed that of the corresponding Lexmark toner cartridge, the 50F0Z00 imaging drum unit works out incredibly economical and needs changinging rarely.Lexmark estimate that this 50F0Z00 black image drum will need changing after 60,000 top quality prints. Lexmark are so confident in the quality of the 500Z black image drum that they offer a full warranty directly.