T5 fluorescent light bulbs are a type of linear fluorescent lamp with a 5/8 inch diameter. They are smaller in size and more energy-efficient than T12 fluorescent lamps. T5 lamps use electronic ballasts, which are more efficient and produce less heat than magnetic ballasts. They have a higher light output per unit length than T12 lamps, making them a popular choice for commercial and industrial lighting applications. They are a good choice for energy-efficient, high-performance lighting.