Genuine OEM Audi Fuel System Union Nut, part number 4F0201375. This white, circular nut is designed to securely connect components within the fuel system, ensuring leak-free and reliable fuel delivery. Made from durable plastic, it measures approximately 17.5cm in diameter. Using a genuine OEM union nut guarantees the correct thread, material strength, and resistance to fuel, preventing leaks and maintaining the safety and efficiency of the fuel system.