Like another reviewer, I bought this for $20. I figured if it didn't work well, the dogs would get it. I had the worst night's sleep of my life. There are four "compartments." It's just like another reviewer wrote. If you put it on the bed correctly, there are tunnels between the baffling compartments. If you switch the position, all you do is shift the tunnels. When I slept on this, I woke up in the middle of the night because there was no support. I tried stuffing the tunnels, and that didn't work. Are we all receiving the same item? How can so many reviewers find it heavenly, and so many other reviewers find it at a level below purgatory? I'm truly perplexed.