I bought two of these for home and office. I have used just the ball in the past so I thought these would be great. They had the height I needed to be able to use them at my desks, the balls are just to small. They are rock hard, no matter how much air you take out of them. The hardness ended up compressing my back and neck so within a short time I would end up with a headache. I am returning them for a small fortune because they are soooo heavy. I am back to using a hard chair at my desks and no headaches :)
I had been suffering from a pulled back muscle for weeks. My old work chair had always been uncomfortable, since I have to sit for long periods of time, so I decided to buy this. I love that I sit up instead of slouch and I can actually stretch my core while I am sitting and working just by moving my middle! My back pains subsided quickly, I believe because of the posture and gentle chair stretching. My rear did take a couple days to adjust, lol, but again, new muscles are happily being employed for work. I also like that the height is adjustable so I can use it with my desk raised. I do switch out with both chairs throughout the day but I have to say, I highly recommend it!
From the moment I sat on this chair my back pain disappeared. The firmness of the 1/2 ball takes some getting used to on my behind nerves but I absolutely LOVE it!! Now all I need is a desk extender so I can either sit or stand whenever I want.