Plug these testers into any car connector and you will have an instant test of running light circuits. Features LED display to show completed circuit for the running lights left turn signal and right turn signal. Auxiliary and electric brake circuit are included on the 6-way tester and auxiliary, electric brake and battery charge are included with the 7-way tester. One piece units with internal ground. Proper installation and set-up of a brake control, when a trailer is not readily available, is possible with the 7-way tester.