Genuine OEM Audi Engine Timing Chain Tensioner, part number 0P2109218B. This crucial engine component is responsible for maintaining the correct tension on the engine timing chain, which is essential for precise valve timing and smooth engine operation. It is positioned within the engine's timing drive system, applying constant pressure to the chain. The tensioner measures approximately 0.065 meters in length and weighs 0.12 kg. Choosing a genuine OEM timing chain tensioner ensures factory-specified spring rates, hydraulic damping, and material quality, which are critical for preventing timing chain slack, noise, and potential engine damage.