Quick Check: This trailer tester is designed to test 7-pin plugs and sockets on both cars and trailers. It quickly indicates whether a fault lies in the car's or trailer's wiring, effectively diagnosing connection problems with 7-pin plugs and sockets. European Universal Standard: This universal 7-pin trailer tester meets European CE and RoHS certifications, is suitable for European vehicles, and can effectively diagnose lighting connection problems. Reliable Quality: This 7-pin trailer tester offers safe and reliable performance, a practical design, and convenient use. It is also easy to store. Can be used with trailers, motorhomes, caravans, bike racks, the test requires a 9V battery (not included). Easy to Assemble - Made of high-quality ABS and copper, its frosted surface is durable and reliable, ensuring maximum strength and durability for long-term use. One side connects to a 7-pin plug and the other to a 7-pin socket; it can also be used with a 13-pin socket with the adapter.