Model 123 Rev C Back Pressure Regulator, Graphite/NBR Gaskets; 1/2" Line Size; Sales Kit B; Stainless Steel Body With Stainless Steel Spring Chamber; S40V Trim: 316 Stainless Steel With Fluorocarbon Elastomer (FKM) Seat, Fluorocarbon Elastomer (FKM) Diaphragm;