Wiring Harness 5 Flat | etrailer Plug the 4-pole connector into your vehicle and connect the wire leads to get 12V power, electric brake protects connector from the elements Simple installation Wiring harness plugs into existing 4-way flat connector and hardwires to existing wiring Specs: Harness length: 12" Wire configuration: Green. Wiring Adapters. Single-Function Adapter Wiring Harness 5 Flat | etrailer Thousands of wiring harness 5 flat reviews, same day shipping. Best wiring harness 5 flat selection available. Lowest price guaranteed. Easy online or Hopkins Wiring Harness with 5-Pole Flat Trailer Connector - Vehicle End - 5' Long - HM37908 (4) Our Price: $ 8. In Stock.