Model DA1 Rev E Pressure Reducing Regulator; 4" Line Size; Stainless Steel Body With Stainless Steel Spring Chamber; NR NACE Trim, Polyurethane Seat, BUNA-N Diaphragm, BUNA-N Static Seal, Elgiloy/PTFE U-Cup Dynamic Seal; OPT-30: Mates With ASME 300 Raised Face Flanges; 10-40 PSIG Range Spring; External Sensing; OPT-40: Construction Per NACE Standard MR0175