For your Brother printer, you'll need both a toner cartridge and a drum unit. The drum unit transfers toner powder from the toner cartridge to the page. This usually happens after the drum unit has been used for a couple of toner cartridges. Brother DR-420 drum unit capacity of 12,000 pages and needs to be replaced after the use of 3 or 4 replacement toner cartridges. Linkyo offers compatible replacement toner cartridges online with a 100% Satisfaction Guarantee in print quality.