Automotive7Pin to 13Pin Towing Trailer Tow Bar Caravan Light Wiring Circuit Tester Plug Socket UK. 1 Piece Trailer Plug Socket Tester. Trailer tester for 7 pins plug and socket connection. -Just plug the tester in the 7 pin socket or the 7 pin plug of the trailer or caravan and press the yellow button on the side of the tester.
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