LuxStar 2ft. 4 Tube Fluorescent Grow Light Kit (Grow Blub)Hydroponic systems need a tremendous amount of light, and the four foot T5 grow light helps deliver the same. It gives out 6500K color temperature, thus imitating the natural sunlight properties. The fixture's output is controlled with the attached ballast, which makes sure that there is a steady flow of current, so during fluctuations, the grow bulb does not get damaged. UL Certified: The certification means that the grow light kit has been evaluated