Extra Long, Heavy-Duty Circuit Tester Long 7 probe shank allows access to difficult to reach areas for testing electrical circuits and locating shorts, grounds, and open circuits. Features and Benefits. 12-foot, heavy-duty, red coil cord lead.. Checks 6- and 12-volt systems.. Ergonomic, slim designed clear handle.. Bright red, slim style replaceable bulb.. Positive contact molded strain relief.. Heavy-duty, stainless steel probe with insulated shaft.. Heavy-duty clip with positive soldered connection. 3639