Each of our Pro Lock Extension Cords are molded with our unique and patented ProLock female locking connector for indoor and outdoor use. When a standard extension cord with a 15A-125V, 3 conductor male plug is inserted into our Pro Lock connector, it won't pull apart. This prevents accidental disconnects that result in an inconvenient loss of power. Simply pull down on the connector collar to disconnect the extension cord. Heavy to ultra heavy use industrial grade.