Model "31-N" Low Press Reducing Gas Service Reg. Graphite/Nbr Gasket; 1/2" Body Size,No.2 (0.125") Orifice; Wcb Body,SST Lower Case,Wcb Spring Chamber,Arrangement/Position 3,;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; Npt Screwed; 8.0-12.0" Wc Range Spring; Opt-25: 1/4" Npt Spring Chamber Vent Tap; Opt-56: Special Clean Per Spec #S-1542