I have a 2-20 watt version of this, and it uses the slim ballasts. Bought it because it could go in front of a cupboard mounted against the ceiling. It's so thin, the door opens below it, with only a fraction of an inch to spare
I think I've seen these at someone's house; they had VERY slow starters and looked to have T12 lamps (a F15T12 will work in an F15T8 light and vice versa right?)