Reduce system pressure upon even a partial obstruction. Used in conjunction with an unloader valve, your pumping system actually has two safety relief valves. Brass construction with Stainless Steel ball and press formed seat. Inlet ports are 1/4" or 3/8" MPT. Valves can be reset in the field if necessary. 160 Deg. F. maximum temperature. Outlet is 3/4" FPT.