Low wattage (approx. 1 watt) LED bulb is clear when Off and glows blue when On with a light out put of a normal bulb. A direct replacement for most cars fitted with the “239” tubular (festoon) light bulb. Overall length is 38mm and the diameter is 11mm. The four bright LED’s glow blue when lit; the bulb is polarity sensitve so if it does not light rotate 180 degrees.These bulbs are not “E” marked. Because of the low power consumption LED bulbs can trigger a bulb failure warning on some cars.