The special Reverse “Y” Adapter features special power isolation circuitry so if one plug is connected to a receptacle, the second plug is isolated so no power flows through it. It provides 50A 125/250V power from 2 30A 125V receptacles. Female end has a sealing collar system.Note: Reverse “Y” will NOT work with 50A, 125V, 3-wire inlets. Power is provided in both circuits to the 4-wire inlet, but the dock side receptacles limit the current in each circuit to 30A. The two 30A 125V receptacles must be supplied from a single power source providing from 208V to 250V between them for proper operation.