Buyers Products Pressure Protection Air Valve should be installed when adding air accessories such as air tailgate latch, air shift PTO, or air lever controls. This valve is designed to protect the air brake system so that a leaking accessory component or accessory airline rupture cannot fully drain the air system. These valves have ¼ NPT inlet and outlet ports for easy connection and are designed to open at inlet pressures above 70 PSI, and close at tank pressure below 70 PSI. b6451005:/b Plated steel construction. Compares to Meritor® R986039 and Tramec Sloan® 401207. b6451040:/b Aluminum construction. Compares to APSCO® PP-470.