It can be used on many Applications fitted with Unit N 7 pin plugs and generally fitted on Trailers, Caravans, Cars, Truck etc. The Tester is designed to indicate a faulty wiring or blown bulbs\/ light in the wiring on your trailer, caravan or horsebox with a Six Light LED system. Quick, easy and very simple to use Feature - Color: Black. - Material: Plastic and metal - Size: 13. 5x7. 5x4. 8cm - Compatible with standard 7- way trailer. - LED indicator for circuit continuity tests. - Plug- n- Play easy installation. - Compact and small- easy to put away - Quick, easy and very simple to use - Warm Tip: Dear buyer, Due to lighting effect, monitor s brightness, manual measurement and etc, there could be some slight differences in the color and size between the photo and the actual item. sincerely hope that you can understand Thank you - Color: Black. - Size: 13. 5X7. 5cm. Package Including 1 x Trailer socket