This Air Cooled Volkswagen Headlight Switch installs into your dash with a 10mm dash nut escutcheon and has a 5mm threaded post for a knob. The headlight knob has 3 positions (off / parking-running lights / headlights-running lights) as well as a rheostat control (twist the knob at the second or third position) to dim or brighten the interior lights. The switch operates on 6 and 12 volt systems.