Product Details: Equip your semi truck to be Ready for the Road Ahead™, with the Bendix ST-4™ 250 psi Safety Valve, a key device that increases overall safety standards. To prevent over pressurization, this replacement component relieves excess pressure from a vehicle once it surpasses a set level. Built with an innovative system to prevent the air compressor from damaging the brake system. FleetPride is your First Click in Heavy Duty®.