Keep your office laser printer performing just as it should and ensure your printouts remain the best-possible quality with this genuine Brother DR-340CL Drum Unit Pack. The DR-340CL is simple to install, reliable and long-lasting, ensuring that print problems won’t slow you down. Brother laser printers require both a drum unit and a toner cartridge. The toner cartridge contains powder (toner) used for creating letters and images. The drum unit transfers the toner to the paper. You need to replace the drum unit when the printer displays the “replace drum” error message.