The ProClass 7-Blade to 4-Wire Flat Trailer Light Wiring Adapter with LED Wire Tester is the quickest and easiest way to make electrical connections when hauling a trailer that has a different wiring configuration than the vehicle. This adapter is ideal for trailers that require a 4-wire flat connection but have a 7-blade towing vehicle connector. The adapter connects taillights, brake lights, turn signals, and ground. The single housing design plugs into your vehicle's electrical socket and requires no wiring. Includes a built-in LED light tester to ensure all light functions are properly working. It provides an ergonomic, durable plastic construction that is corrosion-resistant to withstand extreme weather.