You simply cannot operate a mono laser printer without a functioning drum unit - like the Samsung R304 - being installed. With a page yield that far exceed that of the corresponding Samsung toner cartridge, the MLT-R304 imaging drum unit works out incredibly economical and needs changinging rarely.Samsung estimate that this R304 black image drum will need changing after 100,000 top quality prints. Samsung are so confident in the quality of the MLT-R304 image drum that they offer a full warranty directly.