MODEL "31-N" LOW PRESS REDUCING GAS SERVICE REG. GRAPHITE/NBR GASKET 3/4" BODY SIZE,NO.6 (0.375") ORIFICE; WCB BODY,SST LOWER CASE,WCB SPRING CHAMBER,ARRANGEMENT/POSITION 3, 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; 11.0-16.0" WC RANGE SPRING; OPT-25: 1/4" NPT SPRING CHAMBER VENT TAP;