Model "D" Pressure Reducing Regulator,Tfe Gaskets (Opt-45); 1/2" Size; Sales Kit B; Bronze Body & Spring Chamber; B4 Trim: Brass With Tfe Seat,Fluorocarbon Elastomer (Fkm) Diaphragm; Opt-4: Stabilizer (Recommended For Gaseous Service Only); Opt-55: Cleaned For Oxygen Service Per Spec #S-1134