Model DA2 Rev E Differential Pressure Reducing Regulator; 1/2" Line Size, OPT-81: Full Diaphragm Support Construction; Carbon Steel Body With Carbon Steel Spring Chamber, 1/8" Petcock Vent; PB 17-4PH Stainless Steel Trim, 316L Stainless Steel Cage, Polyurethane Seat, Fluorocarbon Diaphragm, Fluorocarbon Static Seal, Stainless Steel/PTFE U-Cup Dynamic Seal; OPT-30: Mates WIth ASME 600 Raised Face Flanges; 5-20 PSID Range Spring; Internal Sensing; OPT-65A: 1/4" NPT Double Tapped Spring Chamber