Model 1049 Rev A Pilot Operated Vent Valve; Stainless Steel Body; 4" Inlet X 6" Outlet Mates With ASME 150 Flanged End Connections; Fluorocarbon Elastomer (FKM) Soft Seats; Standard Configuration With Internal Sensing And Pilot Exhaust To Atmosphere; Fluorocarbon Elastomer (FKM) Actuator Diaphragm; 12.1" - 18.0" wc Pressure Range; Special Lift Brackets