When I built my 48" light box, I used pre-assembled shop lights--they are the metal lights one hangs above a work bench that plug directly into the wall socket. I priced buying all the parts seperately, and found shop lights cheaper. I got mine at Home Depot. They were around $16 each (sorry I don't remember the exact price). There are expensive ones, and there are cheap ones. I got the cheap ones. But they still have the electronic balasts. One big benefit, no additional wiring. I pluged the units into an outlet strip, which goes into the timer.