Single bladder of air. It is not the Air Hawk and is not an Air Hawk copy. However and for me, there simply was not $150 difference between the single bladder Bunsaver and the multi-bladder Air Hawk after I tried them both.
Again and only to me, $160+ is getting awfully close to the cost of a new seat. If you going to spend that kind of money, may as well just do the right thing and get a different seat.
Now, I have also tried both the Corbin Close and Canyon and like both. I will, however, hold out for a new Russell or (now) for the 2006. Seat is different.
Still, for $10...try the bunsaver.