THIS LISTING IS FOR A AIR COMPRESSOR PILOTED UNLOADER VALVE WITH BUILT IN CHECK VALVE, MOST COMMONLY USED ON GAS POWERED AIR COMPRESSORS. THE PILOT VALVE IS SET FOR 140-175 PSI FROM FACTORY ON THIS VALVE, BUT CAN BE ADJUSTED IF NEEDED 30-40 PSI HIGHER OR LOWER. THIS VALVE HAS A 1/2" FEMALE NPT AIR INLET AND A 1/2" MALE NPT AIR OUTLET. THERE IS AN 1/8" PORT ON THE SIDE FOR A THROTLE CONTROL VALVE OR CABLE. ALSO ON THE SIDE OF THE VALVE THERE IS A 3/8" FEMALE NPT OUTLET TO RELEASE THE AIR ONCE COMPRESSOR REACHES FULL PRESSURE WHICH COMES WITH A 3/8" MALE NPT AIR MUFFLER TO HELP REDUCE NOISE, THAT CAN BE REMOVED IF NEEDED. THE PILOT VALVE HAS A TOGGLE LEVER ON THE TOP THAT CAN BE PUT IN THE UPWARD POSITION FOR LOAD FREE ENGINE START OR THROTLE CONTROL. PICTURE OF THE VALVE HAS A DIAGRAM TO HELP UNDERSTAND MORE CLEARLY IF NEEDED. ALSO IF YOU HAVE ANY QUESTIONS PLEASE LET US KNOW. THANKS AND HAPPY SHOPPING.