The 'NUT FOR BELT DRIVE PULLEY Citroen 11CV PERFO' is a specific automotive part designed for the classic Citroen 11CV with the PERFO engine. This nut is essential for securing the belt drive system to the pulley, ensuring proper operation of engine components such as the alternator or water pump. Made from durable material, it offers optimal grip and stability at high speeds. Replacing this nut can prevent wear and potential damage to the engine drive system. Ideal for restoration projects or maintenance of classic Citroen vehicles.