This listing is for a 190 PSI air compressor safety relief valve, also known as a pop off valve. This valve is NB / UV certified. The relief pressure of this valve is set at 190 PSI and is accurate within + or - 3% of the set pressure. Specifications: This valve will relieve 91 SCFM Valve Inlet Threads: 1/4" Male NPT (measures about 1/2" in diameter) Total Valve Length: 1-5/8" Installation Wrench Size: 9/16" Features a silicone rubber soft seat seal to prevent air leaks Max temperature: 250° F Solid Brass Construction Made in the U.S.A