This tester has a socket at one end to plug into the 13-pin trailer plug and at the other end to plug into the 13-pin maain plug.
Includes a 7 to 13 pin adapter.
9V battery, which quickly indicates if there are problems with the wiring of both the car and the trailer.
Can be used to check lights on caravans and bike racks.
It has two outlets, one for the outlet plug from the car and one for the inlet plug from the trailer.
