If you have any back issues these are great.
I had back surgery that didn't go well. I'm now doing Pilates, hoping this will help. When I'm laying flat on the reformer, the instructor uses a wedge under my back.  I bought these from Amazon. I actually have one of them on my office chair and another on the chair I sit the most in the house.  I'm thinking of sleeping on one, but haven't yet.  If you have any back issues these are great.
Rating: 5 stars