This is a 25 ft Wiring harness for replacing your old or worn out harness on your Boat Trailer. This is a standard 4 Flat Harness with a Ground Wire. This Harness uses the standard White, Green, Yellow, and Brown Wires to successfully connect to your side-marker and tail lights. The Functions of these wires are as follows: White ( Ground Wire), Green ( Right Turn), Yellow ( Left Turn), and the Brown Wires Operate the Left and Right Running Lights. Each wire is 25 ft long, except for the ground wire, which is designed to mount on the trailer tongue. This is a 'wishbone' style harness. It sends (1) brown wire, and (1) yellow wire down the left side of your trailer frame, and (1) brown wire and (1) green wire down the right side of your trailer frame. This wiring harness is most common on small to average sized boat trailers not operating disc brakes. We have the 5 Flat Version of this harness if you are needing it for Disc Brakes.