Genuine OEM Volkswagen Coolant Breather Line, part number 4M0121081CS. This line is a critical component within the engine cooling system, responsible for managing the flow and temperature of coolant in the breather circuit. It is a long, rigid pipe, approximately 0.795 meters in length. Genuine OEM coolant lines are engineered for precise routing, proper fluid resistance, and durability under engine operating temperatures and pressures.