Model "31-N" Low Press Reducing Gas Service Reg. Graphite/Nbr Gasket; 1" Body Size,No.6 (0.375") Orifice; Cf3m Body & Lower Case,Wcb Spring Chamber,Arrangement/Position 4,;Standard Construction Includes Internal Sensing Unless Option - "Es";Is Specified; S40t Trim: 316lSST Internals, Tfe Seat, Buna-N Diaphragm With Cotton;Insert W/ Tfe Cover, Graph/Ptfe Load Ring,No Oxygen Service; Opt-30: 150 Lb Raised Face Flanges; 7.0-11.0" Wc Range Spring; Opt-Es: External Sensing Connection