Fuel Tank Accessories LLC Locking Diesel Fuel Caps are built in the USA. Made from high quality aluminum, and manufactured to prevent fuel theft from HD ' MD Truck Fuel Tanks. Offering 10 different models, these locking and non locking Diesel Fuel Caps fit most all Over-The-Road fuel tanks including Volvo, Mack, International, Kenworth and Reefer fuel tanks. These may be used with Fuel Tank Accessories "Anti Siphon" devices for extra fuel theft protection.