3/16ths hole ..... the old harness has nothing in it. the new one has the black wire outside and inside looks like white/pink stripe... i hate wiring. i have hi/lo headlights,turn sigs,brake lights,emerg flashers,radio ,clock starters working heat/fan .... no-parking/tail lights ,side markers,or tag .. dash or dome tag or reverse. going to put some fuel in and see if i have spark!