Genuine OEM Audi Engine Belt Tensioner, part number 06M903133AC. This essential component maintains proper tension on the engine's drive belt, ensuring the reliable operation of various engine accessories such as the alternator, power steering pump, and air conditioning compressor. Weighing 1.205 kg, it is a robust assembly. Using a genuine OEM belt tensioner guarantees correct spring tension, pulley alignment, and bearing durability, which are crucial for preventing belt slippage, premature wear, and potential engine damage.