Nextgen (ballast company I went with) offers a 400/600 ballast, suppose to run both 400 and 600 bulbs but I really wonder what the "special" part inside would allow this or are they just putting this on the box to sell more. I sent an e-mail to the outfit I bought my ballasts from and asked them the same question and hopefully will hear something soon. I just wanted to make sure that I read things correctly when it was posted last and could not remember where the hell it was posted lol Googled the subject and everything I read said dont do it the bulb will blow blah blah blah. Bulb I'm not worried about, thats only $24 but if something shit in the ballast I think it would be time to check me into the nutshack and give me the last name of Looneytoon :wtf: