This is an auto-changeover regulator used to combine the first and second-stage regulator setup into one and converting tank pressure to 11" WC. Prevents gas outages by switching supply cylinders over to the reserve/#2 cylinder automatically when the primary/#1 cylinder is empty. 650,000 BTU. Two inlets 1/4" Inverted Flare . Outlet is 1/2" Female Pipe Thread.