The TowSmart ProClass 7-Blade Trailer Light Wiring Connector with LED Wire Tester is the quickest and easiest way to make electrical connections between your vehicle and trailer for towing. The 7-blade connector is commonly used on large or RV trailers and connects taillights, brake lights, turn signals, electric brake, auxiliary power, ground, and reverse lights. The single housing design plugs in your vehicle's electrical socket and splices into trailer wiring to provide asuperior connection. 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.