Equip your semi to be Ready for the Road Ahead , with the Bendix R-14 4 psi Air Brake Relay Valve, a crucial element that contributes to fast and reactive air brakes. This replacement component allows for the immediate application of compressed air to the rear air brakes, by acting as a gateway between the service reservoir and the brakes. Engineered with a durable metal body to withstand extreme pressures and consistent use. FleetPride is your First Click in Heavy Duty .