Actually, the intercooler itself is aluminum, however the pipes are steel. Its ETS' kit. It was a very early kit by them, in fact all the pipes are steel except for one, the 3-thousand pipe, its aluminum. I emailed them about it after the fire (once the coating came off i realized it) b/c i was very confused by this. He said it should have been steel but no big deal. He offered to replace it but i was fine with it.