Original OKI B411/B431 Drum Unit. The drum has an approximate yield of 140 pages. Remember: the drum is not a toner and does not contain toner powder. The drum unit is an essential part of your printer, which is subject to wear and tear just like the toner cartridge. Only change it if specifically requested by the printer. Normally the drum unit is replaced after every 3-4 toner cartridges are used, although this depends on the printer model. Buy the original OKI brand drum for the best possible print quality. If you want to save even more, search Webcartridge search for drum units that are compatible with your printer.