Straight tube fluorescent tubes are divided into specifications according to tube diameter: T12, T10, T8, T6, T5, T4, T3, etc.
The "T+number" combination in the specification indicates the millimeter value of the pipe diameter. Its meaning: one T=1/8 inch, one inch is 25.4mm; the number represents the number of T, such as T12=25.4mm*1/8*12=38mm, this standard also applies to LED tubes/
