U-Line® plugs and receptacles allow the use of electrical equipment in hazardous locations. In non-hazardous locations, the U-Line ECP plug fits into standard NEMA 5-20R and 6-20R receptacles. In hazardous locations, the same U-Line plug is the key to energizing the explosionproof U-Line receptacle. Although U-Line plugs can be used with ordinary receptacles, U-Line receptacles are designed so that they cant be energized by an ordinary plug - ensuring that only safe connections can be made in a hazardous location. Its an convenient, time- and money-saving solution for handheld tools, lighting and other equipment that might be used in both ordinary and hazardous locations. When using a U-Line plug in an explosionproof U-Line receptacle, a twist of the plug makes electrical contact and locks the plug in place with an audible click. 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.