Genuine OEM Volkswagen Coolant Hose, part number 3D2122157A. This hose is a critical component of the engine's cooling system, responsible for transporting coolant between various parts such as the radiator, engine block, and heater core. It is located in the engine cooling system. Genuine OEM hoses are constructed from materials that resist heat, pressure, and degradation, ensuring a leak-free and efficient cooling system.