The Camco Propane Double-Stage Auto-Changeover Regulator with 160,000 BTU per hour capacity 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 inch SAE inverted flare and the outlet is a 3/8 inch NPT female.