Round Rubbolite number 23 rear lamp - 91mm diameter at widest with raised red lens and side number plate illumination lens. two double contact bulb holders fitted offering various bulb applications. a very useful lamp into which user can fit two 21 watt bulbs. base 73mm diameter (with rear protruding bulbholders) x 74mm deep. Uses a BA15d bulb, for spare bulbs please see our B319 (6v) or B335 (12v).