Tail light / stop bulb, 6v (may work on 12v but not tested for long periods) LED volt -ve earth (negative ground) Bay15d( dual filament). Direct replacement for original stop /tail light SMALL GLASS bulb used post war. Bulb has SBC Bay15d base and is shorter in overall length than the original bulb. Red LEDs shining through a red lens is brighter that a similar white LED. The bulb supplied may not look exactly like the picture - depending on available stock. These bulbs draw so little power they can be run off a torch battery but the light output is greater. The light at the top (end) of the bulb is red and the side light is white, for the number plate. This model is only for a negative earth system. No changes to lamps or wiring is required.Total height inc contacts: 35mm; Total width: 19mmOriginal bulb number: 384 1157SBC Bay15d = small bayonet cap, offset pin base, 15mm diameter, double contact (normal British tail/stop)