This TowSmart adapter with Wire Tester is the quickest and easiest way to make electrical connections when hauling a trailer that has a different wiring configuration than the tow vehicle. This adapter is ideal for tow vehicles equipped with a 7-blade connector to be able to tow a trailer equipped with a 4-wire flat connection. Built-in troubleshooting, theLEDs illuminate when stop, turn signals, or taillights are activated. The single housing design plugs into your vehicle's electrical socket and requires no wiring. It provides an ergonomic, durable plastic construction that is corrosion-resistant to withstand extreme weather.