Equip your semi truck to be Ready for the Road Ahead™, with the Fuller- Transmissions 1/8" NPT Ranger Slave Valve Assembly, a key component that pairs with a master valve assembly. This replacement piece regulates the flow of air, successfully control the braking functions of the vehicle. Built with an innovative design to evenly distribute air pressure to brake chambers on a trailer. FleetPride is your First Click in Heavy Duty®.