Patron BUSH-HP-M601-PN is a set of rubber-shaft bushings for HP LJ M601/602 toner cartridges. These small parts hold the shaft in place while allowing it to turn inside the cartridge, supporting the cartridge’s mechanical operation.
The bushing can also serve an electrical role: in some cartridge designs, it conducts current between the electrical contact and the shaft. This set is intended for cartridge service when the rubber-shaft bushings need replacement. The product page identifies the set for the M601/602 cartridge models; it does not specify the number of bushings included.