4 Way Flat & 7 Way Round Trailer Wiring Tester Light Brake Tail Turn Signal 4-Way Flat Tester With LED And 7-Way Trailer Light Tester Takes The Guess Work Out of Connecting Trailers Tests Tail Light; Stop/turn Lights And Ground Plugs Into The Connector of The Tow Vehicle Easy To See Bright LED Indicator Lights LEDs Typically Have A Lifespan of 10+ Years Easy And Quick To Test Trailer Circuits On Most Trucks Heavy Duty Nylon Housing Tests 6 Separate Trailer Light Functions: Turn; Brake; Tail; Stop; Reverse And 12v