F18T8/CW/K30 light bulbs are unusual bulbs often used in appliances or other specialised applications. It comes in various lengths, but this version is 30 inches from tip to tip. Many of these lamps were designed with this type of application, hence the multiple lengths for the same wattage bulb. The length is usually denoted by the number at the end of the description on the lamp itself, such as K30. The coluor of cool white is very similar to standard office lighting white. It's the only colour that's available in this type of lamp. Because it's used in many vending machines or appliances, the colour usually is not so much of an issue except that it is a cool white. Even though this lamp comes in various lengths, this 30-inch version is the most common. It only uses 18 watts and runs on a magnetic ballast, which can also be a consumable item. If you have end blackening on the tube, that often means that the ballast is probably wearing out. It might need to be changed, including flickering where it can't start the lamp.