Product Details: Outfit your semi to be ready for the long haul with fast and reactive air brakes, with the OTR 2-Port Relay Valve with Expertise Built In™. Thanks to its fixed location between the rear air brakes and the service reservoir, this replacement component is able to quickly apply compressed air to actuate the air brakes. Crafted with a rugged metal body to withstand extreme pressures and daily use. FleetPride is your First Click in Heavy Duty®.