The 3/4" Cla-Val Model 55L-60 is a UL Listed, FM approved direct acting, spring loaded, diaphragm type pressure relief valve which can be installed in any position and is designed to open and close within very close pressure limits. 
The adjustable pressure range is 100 to 300 PSI and typical installations are use as a fire pump casing/circulation relief valve or they may be installed downstream of a pressure reducing valve.
By removing and relocating the 3/4" plug in the valve body the new design permits installation in either an angle or straight orientation.