This ball chair is comfortable to sit on and comes with a booklet that details various exercises and stretches you can use the chair for. I'm fairly confident that previous reviewers who were critical of the ball's size did not read the included instructions that come with the ball chair. The instructions specifically point out in bold lettering that it may take 24-48 hours for the ball material to "relax" and stretch to the ball's full size. When I first inflated the ball I also noticed it wasn't quite full size, but after letting it sit inflated overnight I was able to inflate it so large that it was difficult to re-seat (pun intended) into the base, and I had to let a little air out. It seems like it's well-made, and it is easy to assemble. There is no real back support for those who like to lean WAY back in their chairs, but I don't think back support fits with the purpose of this ball, which is to improve posture and comfort.