Model "31-N" Low Press Reducing Gas Service Reg. Graphite/Nbr Gasket; 1" Body Size,No.3 (0.1875") Orifice; Cf3m Body & Lower Case,Wcb Spring Chamber,Arrangement/Position 4,;Standard Construction Includes Internal Sensing Unless Option - "Es";Is Specified; S40n Trim: 316lSST Internals,Buna-N Seat & Diaphragm With Reinforcing;Core,Glass Filled Nylon Load Ring,No Oxygen Service; Npt Screwed; 8.0-12.0" Wc Range Spring; Opt-56: Special Clean Per Spec #S-1542