SPL Horticulture STB 1000 Hydroponic 3Pack 600W Watt HPS MH Digital Dimmable Electronic Ballast for Grow Light Bulb Lamp 600 Watt Ballast Adjustable at 100%, 75% and 50% for maximum efficiency, Up to 30% more lumens than magnetic ballasts for improved yields, Compatible w/ both MH and HPS bulbs Compatible w/ 120V and 240V power supplies, High frequency output results in less power loss (50/60Hz Frequency), 99% Power factor Short circuit protection by automatic power shut off for ultimate safety, Fast lamp ignition by lighting up the bulbs within 1-2mins max, Stable light output by constant lamp voltage,lamps will be flicker free Built in cooling fan and Graduating fin design to minimize ballast temperature, Light weight , High quality 2 year Warranty. Extremely high frequency, works perfectly with standard lamps