Model D Rev D Pressure Reducing Regulator For General Service; 1" Line Size; Carbon Steel Body And Spring Chamber; S40 Trim: 316 Stainless Steel Metal Seat With Neoprene (BC) Diaphragm; NPT Threaded End Connections; 2-15 PSI Range Spring; Opt-4: Piston Stabilizer For Gaseous Service; Opt-25S: Stainless Steel Vented Spring Chamber Plug; Opt-40: NACE Construction Per MR0175