Direct replacement main gear for Bafang Ultra M620 mid-drive motor systems. This OEM-spec component restores full drivetrain engagement and torque transfer when wear or damage compromises shifting performance or power delivery. Essential maintenance part for riders relying on consistent motor responsiveness. Fits Bafang Ultra M620 motors. Verify compatibility with your motor generation before ordering. Installation requires motor disassembly and mechanical expertise—consider professional service if unfamiliar with mid-drive repair procedures.