Hopkins Manufacturing Corporation makes your towing experience simpler and more rewarding through innovation and value. Hopkins offers a variety of towing solutions including vehicle wiring kits, adapters, vehicle and trailer connectors, breakaway systems and much more. Today, more than 40 percentage of retail category sales are generated from Hopkins innovations. Four pole rounds are used in many of the same applications that the 4-wire flat is used, however, 4-pole round do not possess an industry standard wiring code.