Rolling out a great seating solution, the Evolution Chair combines core health benefits with convenience and mobility! Get fit while you sit! Sitting all day, every day, is hazardous to your health. It causes muscle weakness and poor posture putting you at risk for back pain and injury. The Evolution Chair combats problems associated with static sitting by successfully uniting the health benefits of active sitting on a stability ball with the convenience and mobility of a rolling office chair. Naturally encouraging proper spinal alignment, the Evolution Chair relieves spinal compression and strengthens your core muscles - all while you sit. Kit includes base, ball, pump, height extensions and casters. Seat height adjustable from 19" to 23"H.