Oh they get warm alright, but if there is air flow around them it is not a problem. I just checked the temp of one , directly on top of the transformer the temp is 44C/110F. If you trust your wiring skills and don't have idiots in your grow room you do not need a ballast box. I just wire them up open on a board allowing air to circulate around the Transformers. Just make sure there are no exposed contacts as they are live. (all those extra wires on the trans. must be wirenutted seperately). Good luck, looks like a good deal, I paid $200.00 Cdn for the same thing at the hydro shop.