U-Line® Contender® Factory Sealed 20 A Plugs and Receptacles feature a dead front design making them ideal for use with electrical equipment in hazardous locations. The neoprene gasket in the throat of the receptacle seals against the plug or the spring-loaded cover to seal out water, dust and corrosive compounds. Although U-Line® plugs can be used with ordinary receptacles, U-Line® receptacles are designed so that they can't be energized by an ordinary plug.