there 8x39 watt all Geissman i have 1 power chrome midday 6k,1 power chrome actinic plus+ 22k,and 6 power chrome aqua blue + 15k. i guess the reasons for me deciding on t5s was, the heat,they put out less heat than halide and i definitely didnt want to run a chiller or have it get even hotter than it already is in my apartment,bulb life t5s seem to last longer than halides,with the amount of bulbs being ran on the t5 system the spectrum of light can be tweaked a lot more by using different bulb configurations,and most of all the perfect fixture popped up for sale and sealed my decision.