Before hitching a new trailer, its essential to make sure the lights are connected properly with the 7-Way Trailer Light Circuit Connector Tester. Circuit testers are the best at testing your trailer lights. Made with heavy-duty plastic and LED lights for reliability. This product works by plugging in the connector socket of your vehicle and seeing the lights response when using the vehicles turn signals or your brakes. When the socket is getting proper power, the tester's various LEDs will light up corresponding to each wire in the connector. Have peace of mind before you take off on your next trip with 7-Way Trailer Light Circuit Connector Tester!