I am 5'2" and this ball was the perfect size for me. I am new to balance balls but it seemed to be of good quality and it had a nice introductory DVD with it.

Other reviewers mentioned how small the "small" ball was but I went with the manufacturer instructions and bought the ball recommended for my height. It's too small. Wish I had listened to the other reviewers. Exercises on the video that comes with the ball are very, very difficult to do. There are no printed instructions with the ball other than how to inflate it so you have to watch the video to use it at all. Overall, I consider this a waste of my money.

I am 5'4 and this is way too small! I wish I had gotten the medium ball. Other than that it is good, I am a fan of the brand Gaiam.

I followed the weight and height guidelines and purchased the small kit, however, when I inflated the ball and began the program and followed the DVD guidelines, I found the ball was too small. If you are over 5'0 tall, I would bypass the small and order the medium.

Though Abs section is reasonable for intermediate level, all other parts are very easy. If you never tried balance ball and never did much of fitness, than it's for you. Also too much relaxation for me. May be worth to do sometimes.