T8 Fluorescent lamps is an older technology used in lots of Commercial and Residential ceiling and recessed lightsAll T8 Fluorescent lamps are 26mm in diameter, the light output and wattage are directly linked to the length so you cant buy a higher wattage lamp to use in the same fitting.
Often to get more light people use 6500K Daylight lamps. While daylight lamp dont put out more light output, because the light is extremely white human eyes perceive them to be brighter.
Some Fluorescent lamps require a starter and we recommend you replace your starter at the same time as your lamp. You can see our range of Starters here: Fluorescent Starters