Genuine OEM Audi Alternator Rib Belt, part number 038903137T. This multi-ribbed belt is a crucial component of the engine's accessory drive system, specifically designed to transmit power from the crankshaft to the alternator. Its primary function is to drive the alternator, which generates electrical power for the vehicle's systems and recharges the battery. Constructed from durable rubber and composite materials, it weighs approximately 0.143 kg. Using a genuine OEM belt ensures correct length, tension, and material composition, providing optimal power transfer and a long, quiet service life.