The Marinco 301ELRV is an Easy Lock 30 Amp, 125/250Volt Standard Inlet, which features the Easy Lock™ System. It has been designed to make hook-up faster and easier. Just connect the cordset (with an Easy Lock™ locking ring installed) to the inlet and turn the locking ring less than a quarter of a turn. The tabs on the locking ring lock into the inlet for a positive watertight hook-up that eliminates any chance of cross threading.