You have to remove the normal seat cushion to put this in. It is only a piece of foam with some covering it. I have used the seat with the cushion removed on track with no other padding, and it was fine. If you don't want to cut and remove your seat cushion, possibly snapping clips in the process, buy a racing seat.
nb. For sale two Sparco EVO racing seats, and Sabelt 6 point harnesses. Have been sat in by me, so garanteed to make your car faster.