Automatically redirects LP gas vapor flow from an empty designated service cylinder to a reserve cylinder without interruption. Green indicator dome changes to red when the service cylinder needs to be filled. 1/4" Inverted Flare Inlet Connections 3/8" FPT Outlet Connection Zinc Die Cast Molded Rubber Diaphragms UL Approved 2nd Stage Relief Mechanism Per UL 144 Powder Coated