Description Reviews MILSPEC INDUSTRIES PRO LOCK Each of these Pro Lock Extension Cords are molded with a patented Pro Lock connector. When a cord with a standard u-ground 15A-125V, plug is inserted into the Pro Lock connector, it locks and won't pull apart. This prevents accidental disconnects that result in an inconvenient loss of power. To release, simply pull down on the connector collar to disconnect the cords. Milspec Industries have added a patented "CGM" Continuous Ground Monitoring system to the Pro Lock connector that indicates there's ground continuity in the cord for added safety.