Old thread, I know, but I am only posting this message so that others who come upon this old thread do not make the mistake of doing what was mentioned here by the original poster re: 430 watt bulb being used with a 400 watt ballast. To be more precise, I am responding to the original posters idea of buying an Eye Hortilux bulb to use with his 400 watt *DIGITAL* ballast. I have read numerous times that you can NOT use Eye Hortilux bulbs on*DIGITAL* ballasts. Apparently, that Eye Hortilux bulbs ONLY work on the older magnetic ballasts and are NOT recommended for use on a digital ballast as there is the potential for it to blow up the bulb.