6 Round To 4 Flat, Electrical Circuit Adapter, Use In Towing Trailers When The Vehicle & Trailer Have Different Electrical Connections, If Vehicle Has A 6 Way Round Connector & Your Trailer Has A 4 Way Flat Style Connector Used For The Trailer Lights, Insert This Product Into The Vehicle 6 Way Round Connector & Plug The 4 Flat Trailer Connector Into It To Operate The Lights, Use Only On 12V DC Vehicle Circuits.