Model 1049 Rev A Pilot Operated Vent Valve; Carbon Steel Body; 4" Inlet X 6" Outlet Mates With ASME 150 Flanged End Connections; FFKM 1 Soft Seats; Option 10: Internal Sensing With Pilot Exhaust Tubed To Main Valve Outlet And Backflow Preventer; Fluorocarbon Elastomer (FKM) Actuator Diaphragm With FEP Liners; 36.1" - 41.7" wc Pressure Range