Just recently I was looking for an alternative to the 600w MH "conversion" bulb I was using. There are no standard MH bulbs in 600w size. On another board (yeah I sleep around) someone mention these PSMH (pulse start metal halides) bulbs, and thery are very interesting. They come in various Kelvin tempertures like fluorescent tubes, ie 3K, 6.4K etc.

Unlike CMH bulbs that only work in magnetic core ballasts, these only work in some (certified) electronic and digital ballasts. I would have bought and tried one, except they did not have the K temp I wanted in stock, so I moved on.

Here's the link for info purposes: Sun Pulse - Home.