The Bendix 1/4" NPT Inlet Port 150 ± 8 psi ST-3 Safety Valve is designed to protect your system from over-pressurization. This valve automatically releases excess air pressure at a preset level and then resets and seals off the system once the pressure drops to a safe level. It is made of premium quality materials for durability and long life. The inlet port is 1/4-18 NPT and the vent is 0.125". This safety valve is a must-have for any system that needs to be protected from over-pressurization. FleetPride is your First Click in Heavy Duty®.