Install a genuine OKI Black Toner Cartridge (44661802) for brilliant results and consistent reliability from your OKI B840 laser printer. When the current cartridge is running low, you'll notice faded print or the message EP Toner Low on your printer's display. Order a replacement cartridge and replace it when you see the Toner Empty message. This standard yield toner cartridge is packed with enough black toner to print 20,000 pages.