Model D Rev C Pressure Reducing Regulator With Graphite/NBR Gaskets; 1/2" Size; Cast Iron Body & Spring Chamber; Bb Trim: Brass With Buna-N (Nbr) Seat,Buna-N (Nbr) Diaphragm; Npt Screwed; 2-15 PSIG Range Spring; Opt-25p: Screen For Spring Chamber Vent