Linkyo Replacement Brother TN-420 provides a sharp monochrome (black) text with a standard yield of 1200 pages. All the toner cartridges have to be inserted into the Brother DR-420 drum unit in order to operate efficiently. A drum unit has a capacity of 12,000 pages and needs to be replaced after the use of 3 or 4 replacement toner cartridges. In addition, our compatible replacement toner cartridges ensure a 100% Satisfaction Guarantee.