Get Ready for the Road Ahead with the Haldex 3/4" Reservoir FF2 Full Function Trailer Valve, a replacement product designed for a wide range of pneumatic applications. To provide your vehicle with the proper brake engagement, this single valve system regulates the supply of air throughout the hydraulic system. Crafted with built-in pressure protection and anti-compounding functions for enhanced performance with running and idle engines. FleetPride is your First Click in Heavy Duty .