Genuine OEM Volkswagen Vent Hose, part number 03D103641S. This hose is part of the crankcase ventilation system, designed to route blow-by gases from the crankcase back into the intake system for re-combustion, thereby reducing emissions. It connects various components within the engine bay, often to the cylinder head or valve cover. Made from heat and oil-resistant rubber. Genuine OEM vent hoses maintain the correct internal diameter and flexibility to ensure proper crankcase pressure regulation and emission control.