Genuine OEM Audi Rib Belt Tensioner Pulley, part number 059903341F. This critical component is responsible for maintaining the correct tension on the engine's serpentine or rib belt, which drives various accessories like the alternator, power steering pump, and air conditioning compressor. Proper belt tension is essential for efficient power transfer and to prevent belt slippage or premature wear. Weighing 0.1697 kg, this pulley ensures smooth operation. Genuine OEM pulleys provide precise bearing tolerances and durable construction, crucial for long-term reliability and preventing costly accessory failures.