Quick Check --- This trailer coupling connector has one side to connect the 7-pin plug of a trailer and another side to connect the 7-pin plug of a car. This tester quickly indicates whether a fault exists in the car's wiring or the trailer's wiring, which can effectively test the problem of 7-pin plug and socket connection. European Universal Standard --- Approved Europe CE, ROHS certification, ensures maximum strength and durability for long-term use. Such a practical trailer testing tool you will need. Reliable Quality --- The 7-pin trailer tester with safe and reliable performance, reasonable design. Smooth appearance, practical use. The trailer tester's socket is widely suitable for caravans, RVs, vehicles, trucks, trailers, etc. The tester requires a 9V battery (not included) High Performance --- The car trailer socket tester is made of high-quality ABS and copper material, frosted surface, durable and reliable, ensures maximum strength and durability for long-term use. One side connects to 7-pin plug and the other to 7-pin socket, can also be applied to 13-pin with adapter.