PRESSURE RELIEF VALVES by GIANT PUMPSProtect pumps and other pressure components from over pressurization. After removing the dangerous high pressure from the system, they are able to be reset, but should be replaced as frequent use minimizes their effectiveness. They should be used whenever a pressure actuated unloader is used as these devices can eventually fail over time. Made in the USA Adjustable 10 GPM max 150 degree F max 3 8" Available In: 500 1200 PSI (Silver) 1200 2400 PSI