T5 tubes measure 16mm in diameter. They're among the more versatile of the size categories, being suitable for lighting everything from schools and office buildings to aquariums. Often installed in new and refurbished buildings, they're energy-efficient, long-lasting and available in a variety of formats, from the traditional long tube to circular styles. One advantage of T5 tubes is that they can be installed in one continuous run on a ceiling, which isn't possible with the larger T8 size. T5 tubes also tend to give some of the truest colour temperatures, so whether cool or warm, you'll get a great effect with these lights.