Reset gear and side end cap for use in Brother TN-420 / TN450 toner cartridges. This gear is only needed if you are refilling STARTER cartridges for the Brother TN420, since the starter cartridges don't always have this reset gear installed. The printer displays a "toner life end" message if no reset gear is detected. A reset gear must be installed on any used TN-420 / TN-450 starter cartridge in order for the printer to function properly once the cartridge has been refilled and re-installed in the printer.
*A starter cartridge is the cartridge that ships free with your printer. If you purchase the cartridge separatley, you will not require this gear.
Each kit contains: 1 reset gear + 1 side end cap + instructions for assembly (easy to do!)