Model "31-N" Low Press Reducing Gas Service Reg. Graphite/Nbr Gasket; 2" Body Size,No.5 (0.3125") Orifice; Wcb Body,SST Lower Case,Wcb Spring Chamber,Arrangement/Position 3,;Standard Construction Includes Internal Sensing Unless Option - "Es";Is Specified; S50n Trim: 316lSST Internals,Buna-N Seat & Diaphragm With;Reinforcing Core; Opt-30: 150 Lb Raised Face Flanges; 8.0-12.0" Wc Range Spring; Opt-25: 1/4" Npt Spring Chamber Vent Tap