Specifications:Main material: ABS and copperColor: blackItem Type: Diagnostic ToolsItem Name: Trailer TesterSize: approx. 20*5*4cmBattery Type: 9V (not included, you need to buy extra)Package size: 20 * 5.5 * 4.5cm / 7.9 * 2.2 * 1.8inPackage Weight: 194g / 6.8ozPackage List:K42161 * 7 Pin Trailer Tester Tool1 * English Guide PaperFunction & Guide:Trailer (can also be a caravan or a bike rack)Put the plug into the tester connection.Press the yellow button on the side of the tester.If the wiring is correct, all LEDs light up. The function of each LED is (acc lso 1724):1. left indicator (yellow);2. fog light or 12V (blue);3. mass (white);4. right indicator (green);5. Right tail light (brown);6. left brake light (red);7. Left tail light (black). Attention: Pin #2 can be used either for a warning fog light or for a permanent 12V connection.If an LED fails to light up, it's because the corresponding wire is faulty. If all the LEDs fail to light up, the ground wire is damaged or all the bulbs are faulty.Car, camper van1. Place the tester into the car's socket.2. Press the yellow button on the side of the tester.3. If the wiring is correct, all LEDs will light up. Repeat steps 4 as before.You can also test the functions of each pin of the socket.1. Turn on the left indicator (after turning on the ignition key).2. The corresponding LED must flash at the same frequency. Otherwise, the left indicator wiring is faulty/broken.3. Repeat steps 1 and 2 for the right turn signal, tail light, fog lights, and brake lights.With an extension of +/- 4 m, you can test the functions of the driver's seat more easily.