This is a 50A 125/250V shore power inlet, most frequently mounted in the boat's cabin side or cockpit coaming.

Easy Lock twist-to-tighten system
Solid cast 316 stainless steel
Soft Touch cap stays open in the upright position
Locking waterproof cap
Rear safety enclosure with strain relief covers wire terminals
Model 6373EL-B includes a rear safety enclosure and wire strain relief; Model 6373EL does not
When closed, inlet exceeds ABYC watertight requirements for boat inlets
UL listed, SA marked, 5-year warranty


Heavy on the technical side...

There are two categories of 50 Amp devices: 50A 125V (50A 3-wire), and 50A 125/250V (50A 4-wire).
The 3-wire devices have a single "hot" leg carrying 50A 125V.
The 4-wire devices have two "hot" legs, each carrying 50A 125V. (50A 250V when combined.)
These two categories are NOT interchangeable.
Never alter the plug of one type of these devices to fit into the receptacle or female connector of the other type.