This is an isolated trailer wiring harness. It is designed to isolate the wiring between the bike and the trailer to prevent electrical feedback into the bike. It also reduces the chance of overloading the bikes taillight circuits. This is a 5 wire harness that gets the power for the trailer lights directly from the battery. It has five relays that are activated by the factory wiring harness. This plug and play harness will fit on all Goldwing 1500's from 1988-2000.