Virtual Sun VS400MH 400-Watt MH Grow Light Bulb High power 400-watts (mh) bulb - 36,000 lumens high output - color temperature: 4,200k Average life span 10,000 hours Mh bulb give out 10% more light than standard bulb - 10% increase of light output = 10 % more plant growth 30% more blue/violet provides better range for your plant Fits all standard 400 watts mh grow light systems