# T8 Tube > A tubular lamp 1 inch (26mm) in diameter, the standard size for commercial fluorescent lighting. LED T8 tubes are direct replacements. **Source:** T8 is the workhorse of commercial and industrial lighting — those 4-foot fluorescent tubes in every office, school, warehouse, and garage ceiling. The "T" stands for tubular, and "8" means 8 eighths of an inch (1 inch / 26mm) in diameter. They use a G13 bi-pin base at each end. LED T8 replacement tubes come in three types, and the distinction matters for installation. Type A (plug-and-play) works with the existing fluorescent ballast — just swap the tube. Type B (direct wire) requires removing the ballast and wiring line voltage directly to the sockets. Type C uses an external LED driver to replace the ballast. Type A is easiest to install but depends on a functioning ballast. Type B is the long-term solution since there's no ballast to eventually fail. The energy savings from replacing fluorescent T8s with LED T8s are significant — typically 40-60% reduction — but the bigger win is maintenance. Fluorescent tubes degrade visibly within 2-3 years and need regular replacement. LED T8s maintain output for 50,000+ hours. ## Specifications | Spec | Value | | --- | --- | | Diameter | 1 in (26mm) | | Common lengths | 2ft, 4ft, 8ft | | Base | G13 bi-pin | | LED types | Type A (ballast compatible), Type B (direct wire) | ## Related Terms - [Ballast](https://ledlightinginfo.com/glossary/ballast.md) — A device that regulates current for fluorescent and HID lamps. When upgrading to LED tubes, you may need to bypass the ballast depending on the tube type. - [LED Driver](https://ledlightinginfo.com/glossary/led-driver.md) — A power supply that regulates current to LEDs, preventing flickering and enabling dimming. Every LED has one — either built into the bulb or as an external unit.