Atto (symbol a) is a unit prefix in the metric system denoting a factor of 0.000000000000000001. OK, this combination brake and taillight is not that small, but with a 13mm diameter the Atto is so small that the lighting surface fits four times on a 1 Eurocent coin. It uses Extreme Optical Transparency technology, providing spectacularly bright lighting lighting. Also available as a white position light that also can be used as front parking light, as well as turn signal. All Atto lights feature a minimalistic M5x6.5 mounting stud and are sold each.