Equip your semi truck to be Ready for the Road Ahead , with the Prima Brake Components E-3 Single Circuit Brake Foot Valve, a crucial component that helps apply / release the air brakes. This replacement reacts to the pressure from a driver's foot to a brake pedal, actuating the flow of compressed air to the brake chambers. Manufactured with top-quality materials that are suitable for single-circuit air brake systems. FleetPride is your First Click in Heavy Duty .