Model 123-1+6+S Rev C Differential Back Pressure Regulator, OPT-40: Construction Per NACE Standard MR0175; 3/4" Line Size, 3/4" Full Orifice; Carbon Steel Body With Carbon Steel Spring Chamber; S40S Trim: 316 Stainless Steel With Metal Seat, Fluorocarbon Elastomer (FKM) Diaphragm; OPT-30: Mates With ASME 600 Raised Face Flanges; 65-160 PSID Range Spring (Inconel X750); Per Spq/Ma Drawing Number 32934