Genuine OEM Volkswagen Alternator Belt Tensioner, part number 038903315AB. This critical component is designed to maintain the correct tension on the engine's alternator belt, ensuring optimal power transfer to the alternator and other belt-driven accessories. Weighing approximately 0.83 kg, it is engineered for durability. Choosing a genuine OEM tensioner guarantees the precise spring calibration and pulley alignment required for vibration-free operation and extended service life of the belt and associated components.