7' CUSTOM WIRING EXTENSION HARNESS7' CUSTOM WIRING EXTENSION HARNESS 7' Custom Wiring Extension Harness (Adds 4 Way, 7 Way RV Blade to Truck Bed) Routes a dual output socket into truck bed while retaining use of rear socket Provides standard 4 way flat and 7 way RV blade Simple plug and play design eliminates the need for cutting or splicing Allows for easy connection of 5th wheel or gooseneck wiring 4 way flat output connects tail lights, brake lights and turn signals 7 way connects