Straight from the lumatek website, even has a good warranty on them:
Lumatek is the worlds leading supplier of Electronic Ballasts to horticulture. With the arrival of Electronic Ballasts, a technological revolution has taken place in energy efficiency for HID lighting. This replacement of magnetic ballasts (a technology more than 100 years old) with electronic HID ballasts is because of the proven efficiency gains. Tests have shown that Lumatek ballasts are up to 30% brighter than some old style magnetic ballasts. Independent laboratory tests have proven that Lumatek ballasts are more efficient than any magnetic ballast known to Lumatek. This means more lumens are produced per watt of energy consumed.
Lumatek is the number one supplier of Electronic Ballast to the hydroponics and horticultural industries worldwide, and is proudly available in at least 13 countries. Lumatek products are sold into government research facilities, major nurseries, top universities and numerous publicly traded companies. This makes the Lumatek range the most proven product in the market, in addition we have the industries best warranty with 5 years covered (3 years full and two years pro-rated).