Trekker USA Anti Siphons prevent fuel theft from HD Truck Fuel Tanks. Built in the USA, Trekker Anti Siphons fit most Over-The-Road fuel tanks using 1.85 to 3-inch ID fuel tank necks including Volvo, Mack, International, Freightliner, Kenworth and Reefer fuel tanks. Much less expensive and more secure than a locking fuel cap. Installs in less than 30 seconds.