Genuine OEM Audi Engine Coolant Reservoir Breather Line, part number 4K1121081G. This line plays a crucial role in the engine cooling system by allowing trapped air to escape from the coolant reservoir. Proper venting prevents air pockets that can lead to inefficient cooling and potential system damage. It connects directly to the coolant reservoir. Measuring approximately 68 cm in length, this line is designed to withstand cooling system temperatures and pressures. Installing a genuine OEM breather line ensures correct pressure regulation and optimal performance of the cooling system.