Safety on the road is top priority. You can be sure your tow lighting is working properly with the Hopkins Towing Solutions 6 to 12 Volt Circuit Tester for 4 Flat Connector 48715. This set tests left/right turn signals brakes and taillights. The red LED light will illuminate if the connection is correct. Quickly and easily confirm if your vehicle 4 flat connector wiring is properly installed and functional. Doubles as a dust cover to keep it handy! This two piece kit also it includes a 6-12 volt probe circuit tester. Instructions are included.