Maro 50a Receptacles & Plugs Sealing Collar With Ring . The 50A shorepower systems are offered in 125V 3-conductor, 2-pole models and 125V/250V, 4-conductor, 3-pole models. Make sure to order matching components, as they are not interchangeable. Non-Metallic Power Inlet is watertight with either white polyester (wp) with marine stainless ...