Genuine OEM Audi Serpentine Belt Idler Pulley, part number 074145278E. This pulley guides and maintains proper tension on the serpentine belt, ensuring reliable operation of engine accessories like the alternator, power steering pump, and air conditioning compressor. It features a durable plastic body with a precision-engineered metallic bearing. Weighing 0.268 kg and with a diameter of approximately 0.09 meters, its smooth rotation is critical. Choosing a genuine OEM idler pulley guarantees the correct bearing quality, material strength, and precise dimensions for quiet, vibration-free operation and extended service life, preventing belt slippage and premature wear.