Genuine OEM Audi Gear Synchronizing Hub, part number 01X311309. This critical internal transmission component is responsible for matching the rotational speeds of different gears before engagement, allowing for smooth, precise, and quiet gear changes. It is integral to the manual transmission's functionality. Weighing approximately 0.288 kg, this hub is a precision-machined metal ring with internal splines. Using a genuine OEM synchronizing hub ensures the correct material hardness, precise tooth profiles, and exact tolerances, which are vital for preventing grinding, extending the lifespan of the transmission, and maintaining optimal shifting feel.