Bought one for myself which is great, and thought i would buy two Kids balance ball chairs for my twins. The chairs were way too small for both twins who are age 12, and the adult chair was very comfortable and much more appropriate. I would say the kids chairs are more appropriate for ages 5-8 or so.
My 4 & 6 yr old nieces spotted my chair and started fighting over it. I suggested we go on line and see if there are kids chairs. Lo and behold in their favorite colors ! They arrived less than a week later. They sent a picture of beaming faces and said " Best present ever" !