T12 is a type of fluorescent lighting bulb. This type of bulb is a common choice for lighting commercial and residential buildings, as it is cost efficient and provides a large amount of light. T12 bulbs operate with two inches in diameter, which is larger than the single inch bulbs. This larger diameter allows for more light to be emitted, making it a preferred choice when high levels of brightness are desired. T12 bulbs are beneficial as they require few replacements, due to their long lifespans. Further, they are available in various wattages so that the user can choose the brightness level that best suits their needs.