Genuine OEM Audi Coolant Reservoir Overflow Hose, part number 8K0121081AE. This hose is a vital component of the engine cooling system, designed to safely route excess coolant from the expansion reservoir. It prevents over-pressurization within the cooling system, which can lead to leaks or damage to other components. Weighing 0.08 kg, this hose features specific routing geometry and connectors. Using a genuine OEM overflow hose ensures proper fitment, resistance to coolant chemicals and temperature fluctuations, and reliable operation of the cooling system.