T5 fluorescent tubes. T5 tubes have a diameter of 16mm and are often used in ceiling, under cabinet lighting or emergency lighting. They are also often used as the light source in illuminated bathroom mirrors and cabinets.
T5 tubes are more efficient than T8 tubes, and are starting to be used instead of the larger T8 tubes in commercial and retail and office lighting.
There is a variety of wattages and lengths available, but the wattage is does not necessarily dictate the length of the tube, so make sure that you know what size of tube you need as well as the wattage.