Gently rounded ergonomic base allows you to move and flex without moving your seat. Exercises legs, back, and abdominal muscles. Increases “Secondary Focus” which allows for clearer thinking. Ideal for students with ADD or ADHD. Patented anti-roll safety ring on base prevents tip-overs and falls. Soft padded cushion for extra comfort. Rubberized coating is non-skid, non-scratch and grips most surfaces. 360 actuator ring to raise and lower the seat. Adjustable seat height is 18" - 25"H. Diameter: Seat 14"W, Base 15". High rise active chair 21"-31.5". Manufacturer Lifetime Warranty.