Powerplant Metal Halide lamps are designed for your plants growth period as they deliver a blue spectrum of light at 4000 Kelvin. Providing your plants with a pure blue spectrum of light will encourage them to become much bushier with thicker stems and lush green growth and this will help to maximize the potential of your plants when you enter your flowering period. Powerplant MH lamps are retro fit and are designed to work with any type of ballast, even if you only specifically have a ballast for HPS lamps, these lamps will still work with a life expectancy of around 10,000 hours. Lumen Output Powerplant MH 250w lamp - 23,000 lumens Powerplant MH 400w lamp - 38,000 lumens Powerplant MH 600w lamp - 51,000 lumens Powerplant MH 1000w lamp - 100,000 lumens