Genuine OEM Audi Engine Vent Hose, part number 4H0121107L. This hose is responsible for routing gases and vapors away from the engine, playing a vital role in the engine's ventilation and emissions control system, often related to the cooling circuit. It is typically located within the engine bay, connecting various components. Made from high-quality, heat-resistant rubber or reinforced plastic, it ensures durability and leak-free operation. Using a genuine OEM vent hose guarantees correct routing geometry, material integrity, and resistance to engine fluids and temperatures, preventing potential leaks or system malfunctions.