cmh have both spectrums and is supposed to have better wavelengths in the red range of the hps and it supposedly puts out less heat. However i find a blue spectrum added hps does better than the cmh imo and no real difference in temps. They are alright, ive got and use one and it does outperform my old normal metal halide bulb, but hps beats it still imo. I just realized something though. He has a metal halide ballast it sounds like and you need an hps ballast for cmh. So my advice was BAD. Sorry i didnt realize my mistake sooner.