2 Stage auto-changeover regulator allows fuel to be supplied by two separate cylinders. Standard equipment on most Trailers and Fifth wheels. It lets you know when one tank is empty and allows you to get empty tank filled while not interrupting service provided by the other cylinder. Easy to use and replaces virtually all other manufacturers' Auto Changeover Regulator. Equipped with two 1/4" inverted female flare inlets x 3/8" female pipe outlet.