Model 31-N Rev A Low Pressure Reducing Gas Regulator; 3/4" Body Size, #2 (0.125") Orifice; Carbon Steel Body, Stainless Steel Lower Case, Carbon Steel Spring Chamber, Arrangement/Position 3, Internal Sensing Unless External Sensing Option Is Specified; S40N Trim: 316L Stainless Steel Internals, BUNA-N Seat And Diaphragm, Glass Filled Nylon Load Ring; Per SPQ 51628 With Special OPT-30: Mates With ASME 300 Raised Face Flanges; 4.5-5.5" wc Range Spring