What kind of tank are you putting this on? I bought one and returned it the next day because I was disappointed with its poor design. I loved how it was so low profile, had two different bulbs, and was 30" (which is very hard to find), but they are not high output lights, they're too close together, and the reflector is terrible (and that's being kind.) I've they would have made these 2x24W HO and gave them individual reflectors, I would have called the LFS back up and had them order a second unit for me. I suppose it would be great for a low-light 20gal long, but that's about it.
Just a word of caution. Good luck!