It's a thin neoprene cover and it makes the crappy spin saddles bearable for a few hours. It also has nice no slip, water proof quality to it. It's also small enough you can fold it and stow it in a jersey pocket.
Downside, it tears easily if you dig your fingernails into it while stretching onto your saddle, but at $11 it's not the end of the world. I'm still using my original one, twice a week for a couple of months.
Just thought I'd offer a heads' up, I am not affiliated with the seller.