The Gaiam(R) Balance Ball Stool provides all-day ergonomic support for a stronger, healthier back. By sitting on the ball, you'll improve your posture and spinal alignment while getting a powerful core-strengthening workout. Sit Strong Anti-burst, dome-shaped Balance Ball seat Micro-motion from instability strengthens core, posture and circulation Stool adjusts from 23" to 31" high to fit most regular and standing desks Lightweight and compact with lockable, easy-glide caster wheels Stable, 360deg base allows easy swiveling movement Includes easy-inflation pump