Model 31-N Rev A Low Pressure Reducing Gas Regulator; 3/4" Body Size, #4 (0.250") Orifice; Carbon Steel Body, Stainless Steel Lower Case, Carbon Steel Spring Chamber, Arrangement/Position 4, Internal Sensing Unless External Sensing Option Is Specified; S40N Trim: 316L Stainless Steel Internals, BUNA-N Seat And Diaphragm, Glass Filled Nylon Load Ring; NPT End Connections; 8.0-12.0" wc Range Spring; OPT-25: 1/4" NPT Spring Chamber Vent Tap