Model Compatibility: Xerox 6255 series printers and compatible models Function: The knob is designed to help with the installation and removal of the toner cartridge, allowing the cartridge to be securely locked into place during operation or easily removed for replacement or maintenance Material: Typically made from durable plastic or other sturdy materials to withstand repeated use Purpose: To facilitate smooth cartridge handling and ensure the toner cartridge remains properly seated during printing Location: Located on the side or top of the toner cartridge, depending on the printer design