Number of Bulbs - This refers to the number of bulbs that your fluorescent fixture is designed to hold.

Color Temp (K) - Color temperature is a way to describe the light appearance provided by a light bulb (lamp). It is measured in degrees of Kelvin (K) on a scale from 1,000 to 10,000. In general, 2,000K will emit a red/orange spectrum which is ideal for the flowering phase of a plants life. A 4,000K - 10,000K color temp will emit a bluish spectrum which is used during the vegetative phase.