Breathable black foam with large pores. We use this 2" size on our fiberglass and carbon fiber seats. This is also the same foam from the same supplier that outfits Bacchetta recumbents. This product is sold in 12 x 12 x 2" basic units. We stock it in a big sheet. If you need something other than the sizes we've listed, just call or email and we can help you out.