The Sun System Harvest Pro 400 watt switchable ballast is the most versatile grow light ballast on the market! It operates either HPS or metal halide lamps with the flip of a switch, so there's no need to buy a new ballast when you switch from the growth to the budding phase of your plants. Its aluminum enclosure is engineered to dissipate heat and keep critical components cool with separate compartments for the coil and capacitor. In the unlikely event a capacitor fails, you can easily change it out with Sun System's "EZ Cap Door." A heavy duty handle makes it easy to carry the ballast or hang it on a wall, while rubber feet reduce noise and vibration. The "Power Pointer" allows the ballast to operate on both 120 and 240 volt systems: Simply unplug the 120 volt power cord (included), turn the Power Pointer arrow down for 240 volt power, and plug in a 240 volt power cord (sold separately).