You simply cannot operate a mono laser printer without a functioning drum unit - like the Lexmark 50F0ZA0 - being installed. With a page yield that far exceed that of the corresponding Lexmark toner cartridge, the 50F0ZA0 imaging drum unit works out incredibly economical and needs changinging rarely.Lexmark estimate that this 500ZA black image drum will need changing after 60,000 top quality prints. Lexmark are so confident in the quality of the 500ZA  black image drum that they offer a full warranty directly.