This is a special low watt bulb for the Marker Light.  The bulb  is 6 volt 4 watt. this bulb is specially manufactured by us and the low wattage requirment is necessary because a higher wattage bulb will create excessive heat in the enclosed Marker Light that the rear of the plastic lens in the Marker Light Door will distort from the heat and eventually melt and then a very expensive Market Light Door is ruined.