I have this one. It's really good for a short period of time, and the body has to be tilted in the right way to keep it in. The problem is that it's firm enough to be a challenge getting in, but soft enough that the slightest contraction of the muscles there collapses the device. If I so much as sneeze, it collapses in on itself. That said, I often use it with a large plug inserted into it to get maximum width out of the experience.