InkOwl Reset Flag Gear Kit for BROTHER TN-720, TN-750, TN-780 Starter Includes the gear, spring, and replacement hopper plug needed to convert a starter TN-750 cartridge to a high-yield cartridge that can be refilled. Comes with easy, detailed, graphic installation instructions. The starter cartridge that is shipped with new printers requires the installation of this gear prior to being refilled. Our instructions will guide you step-by-step through the installation process. If you're planning on refilling the cartridge that originally came with the printer was bought, you'll absolutely need this kit.