U-Line™ factory sealed 15 and 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.