The Double Stage Automatic Changeover Regulator Camper Trailer RV Regulator maintains constant gas pressure and automatically changes from empty tank to full one. Allows the removal of empty cylinder for refill without interrupting propane supply. For RVs with dual pronpane tank hookup. Inlet 1/4″ SAE inverted flare. Outlet 3/8″ NPT female. 11″ w.c.