The Camco Propane Double-Stage Auto-Changeover Regulator is for RVs with dual propane tank hookups. It maintains a constant gas pressure and automatically changes from the empty tank to the full one. It allows for the removal of the empty cylinder for refill without interrupting the propane supply. The inlet is a 1/4" SAE inverted flare and the outlet is a 3/8" NPT female. Allows removal of empty cylinder for refill without interrupting propane supply Allows removal of empty cylinder for refill without interrupting propane supply For RVs with dual propane tanks. Automatically switches from primary to reserve tank when primary is empty Primary cylinder 210,000 BTU/hr capacity; Reserve cylinder 130,000 BTU/hr Double stage design maintains constant gas pressure under changing demand and conditions