What is the difference between a T8 fluorescent light bulb and a T11 fluorescent light bulb?
It is one of several bulb coding techniques. On the T8, the T indicates that the shape of the bulb is tubular, and the last number is the diameter in eighths of an inch (sometimes in millimeters, rounded to the nearest millimeter). A T8 is 8 eighths (1 inch) in diameter. The T11 isn’t a tubular bulb at all but an 11 watt fluorescent spiral U-tube. These are typically used for smaller fluorescent fixtures and flashlights.
