The Mr. Heater Propane Auto Changeover Two-Stage Regulator has two 1/4" inverted female flare inlets and a 3/8" female pipe outlet. It's most commonly used on RVs with a dual tank hook-up to automatically change over from an empty tank to a full one without interruption. It includes gas gauge for monitoring pressure consistency through dual regulators.• For use with propane gas tanks• Automatically changes from an empty tank to a full one without interruption• Gas gauge for monitoring pressure consistency• Zinc construction with solid brass fittings• Two 1/4" inverted female flare inlets• 3/8" female pipe outlet• 11" W.C. setting• 1/2 PSI output Gas gauge for monitoring pressure consistency through dual regulators Two 1/4"" inverted female flare inlets 3/8"" female pipe outlet