Genuine OEM Audi Ribbed Belt Tensioner, part number 045903315A. This crucial component is responsible for maintaining the correct tension on the engine's ribbed accessory drive belt, ensuring efficient power transfer to various ancillaries like the alternator, power steering pump, and air conditioning compressor. It is typically located on the engine block, integrated into the belt drive system. Weighing 1.152 kg, this tensioner features a robust design for consistent performance. Choosing a genuine OEM tensioner guarantees precise spring calibration, durable bearing quality, and proper alignment, which are vital for preventing belt slippage, premature wear, and potential damage to engine components.