Genuine OEM Audi Ribbed Belt Tensioner, part number 06E903133AE. This assembly is designed to maintain the correct and consistent tension on the engine's accessory drive belt, which drives various engine ancillaries. It prevents belt slippage, reduces noise, and extends the life of the belt and associated components. Weighing 0.9 kg, this tensioner is built for durability and precise function. Choosing a genuine OEM tensioner ensures the correct spring rate, damping characteristics, and robust construction, which are critical for the long-term reliability and performance of the accessory drive system.