Trailer wiring sub-harness plugs into the bike's stock wiring harness on one end, and Rivco's own 5- to 4-wire converter or isolator on the other Eliminates the need to cut and splice the stock wiring harness All sub-harnesses require two additional parts for a complete trailer wiring harness assembly: Rivco's 5- to 4-wire converter (PART #3902-0134) and Rivco's Universal Trailer Wiring Isolator (PART #3902-0119) (both sold separately). WIRING HARNESS HD MOLEX