Flame King (ACR6) 2-Stage Auto Changeover LP Propane Gas Regulator 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 Rated for 30,000 BTU Double stage design maintains constant gas pressure under changing demand and conditions Inlets are 1/4" SAE inverted flare and outlet is 3/8" NPT female pipe thread