Gaiam Balance Ball Chair

I've had this chair for 5 years (purchased through Gaiam). Originally bought due to back/ neck pain from working at a computer most of the work day. All pain was gone shortly after using this and has not returned. I still find ways to get sloppy posture when tired, but you get reminded soon enough. :) The quality is good. It's lasted 5 years! A coworker who is rough on chairs and has destroyed several "normal" desk chairs popped her ball after a year or so by throwing herself on it. We considered that "user malfunction". The plastic is sturdy. A previous review had concerns of the ball size. When first inflated, the ball does look small. It takes a few days to expand to a normal size, and will expand more in time. It only needs inflating every few months ongoing.