A few months ago, I bought a set of 4 of the E5x Blue Pop 54W bulbs to run in my Giesemann Spectra fixture. These bulbs are absolutely amazing! They are basically a Reef Brite, but in a T5 housing. However, they are not compatible with a MH fixture that is not fan cooled. My Spectra fixture...
http://www.aquariumspecialty.com/sale-clearance-items?manufacturer=7384
$500.00 fixture for $299.00 150 watt LED fixture...this is below cost and only 2 left in stock. Also we still have a few Euroquatics T5 LED lamps left.