PC- power compact flourescent. Very good lighting for the price. It puts out more than twice the power than normal output flo. in half the space. I have 220 watts PC over a 75gal. reef. and everything is very happy(my torch looks better than any I've seen in any of the LFS's). I plan on adding at least another 110 watts in the near future. It is especially good when heat is a concern, mine run cooler than NO flo.
HTH,
B