Indoor Sunshine is the closest match to natural sunshine. Sunshine is 100 CRI, 5500 K (Kelvin). Indoor Sunshine is 95 CRI 5300 K. If the CRI (Color Rendering Index) is not listed, it's not true full spectrum. Full spectrum light may reduce fatigue, increase mental clarity, provide clearer vision and boost productivity. A two-year school study in Canada with 4 kinds of light reported “lighting systems are not neutral – they have non-visual effects on people.” Students under true full spectrum light tested higher, grew faster, had 1/3 fewer absences and 2/3rds fewer cavities. Sunshine itself is the blueprint for Indoor Sunshine. Could life exist without SUNSHINE? Indoor Sunshine is available in 15 wt, 25 wt, 30 wt, and 3-way bulbs.