Contoured Seat Pad 

This is a closed cell foam pad.  What this means is, it will add more cushion with less compression than other seat pads.  Too much compression can cause you to slide out the front.  Also seat pads with less density will flatten and not retain it's padding quality, causing it to collapse prematurely.

Has tailbone cutout for 1999 - current model Air Chairs. 1 1/4" thickness