Improve Posture & Relieve Back Pain Recommended by physical therapists and chiropractors, our yoga ball chair for office can improve your sitting posture, strengthen your core muscles, and reduce lower back pain to encourage a healthier lifestyle. Stability and Safety- Our yoga ball chair is made of non-polluting and hypo-allergenic material; rated up to 330 lbs. The base keeps the stable ball from rolling around. The 65cm exercise ball is recommended for customers 5'3 to 5'10 in height