Growers Choice SE 500W CMH 3K-RGrowers Choice 3k CMH lamp utilizes a full phase spectrum that is designed to be used in all stages of growth but optimized for bloom. With a Color Rendering Index of 90 the GC 3k spectrum is very close to natural sunlight but with modest blues, extra red and UV light to serve your plants photosynthetic needs during the flowering phase increasing yields and resin production. For use in any standard 500W CMH fixture Produces more PAR per watt than HPS