Lighting & Illumination What does T5, T8, and T12 mean? February 6, 2026 by Myaya | Leave a Comment T5, T8, and T12 refer to different types of fluorescent light tubes, distinguished by their diameter and efficiency. Understanding these differences can help you choose the right lighting for your needs. What Do T5, T8, and T12 Mean in Fluorescent Lighting? Fluorescent light tubes are categorized by their diameter, measured in eighths of an inch. […] Read more ยป