Genuine OEM Audi Engine Chain Tensioner, part number 05A109255A. This critical component is responsible for maintaining the correct tension on the engine's timing chain, ensuring precise valve timing and smooth engine operation. It is located within the timing chain assembly. Weighing 0.09 kg, this tensioner is engineered to exact factory specifications. Using a genuine OEM chain tensioner is vital for preventing premature wear, chain slack, and potential engine damage, ensuring long-term reliability of the timing system.