I'm running a 400w MH std High-Bay setup(magnetic/expensive ballst), been doing just fine. I believe the std bulb for my unit is a MH400/C/U. I think the 'C' is for commercial, and the 'U' is for universal mounting,ie Vertical or horizontal. You do get better lumen output in vertical(base up) position though. The bulb is a 3700K yellowish/orange.

Check this out for progess.. 35 days flowering tonight, these pic are a few days old.. and I've used the same bulb/ballst from seed til now.

http://boards.cannabis.com/closet-ca...-thoughts.html

Good luck dude
Jungl3Jim Reviewed by Jungl3Jim on . help on lights pleas ok i ended up getting 2 light fixtures from a grage sale(homegrown high intensity discharge grow light/high pressure sodium) they have all diferent amounts of wattage marked on the sticker thats on the box. the box plugs in the wall with a normale 3 prong plug and another cord is hooked up to a light socket with a big dome around it. now on that sticker the 400 watt mark is colored in and on the other one someone marked in black marker 400watt MH. is anybody famillure with theese typs of Rating: 5