Genuine OEM Audi Engine Accessory Drive Belt Tensioner, part number 06M903133AA. This crucial component is responsible for maintaining the correct tension on the engine's accessory drive belt, ensuring efficient power transfer to various engine accessories like the alternator and power steering pump. Proper tension prevents belt slippage and premature wear. Weighing approximately 1.07 kg, this tensioner is built to factory specifications. Using a genuine OEM tensioner ensures precise spring calibration and durable construction, critical for the longevity and reliable operation of the accessory drive system.