Genuine OEM Audi Coolant Reservoir Top Hose, part number 3C0121447L. This hose is responsible for transferring coolant to and from the engine's coolant reservoir, playing a vital role in maintaining optimal engine operating temperatures. It is part of the engine cooling system. Made from high-quality, heat-resistant rubber, it weighs approximately 0.0392 kg. Using a genuine OEM coolant hose ensures correct routing, pressure resistance, and material compatibility, preventing leaks and maintaining cooling system efficiency.