FASS Diesel Fuel Systems are the number one preferred Fuel Air Separation System selected for use by Pickup and Class 8 owners the world over. FASS Systems are designed to eliminate Air & Vapor trapped in diesel fuel. Delivering purified fuel without Air & Vapor increases lubricity, which provides extended injector life and maximizes the performance of your engine. FASS products are designed, manufactured, and assembled right here in the United States.