This chair is very useful for stretching, preventing spine disorders, rehabilitation, correcting posture, reducing stiffness and improving circulation. A strong, healthy back is crucial to our well-being and vitality. Featuring a sturdy base designed with 4 rolling wheels, of which 2 can be locked into position, this is the perfect chair for in the home or at the office. Additionally, this chair acts as a shock absorber while you are seated in it and helps to ease your body into an ergonomic position for improved posture. You will appreciate the fact that you can practice stretching and strengthening key muscles without having to visit a gym. This chair offers numerous other benefits and many more when used with a balance ball. This purchase includes a black balance & stability ball as well as a pump to inflate the ball. Manufacture recommends sitting low ,as it is better for your back, but for people who prefer sitting higher for example sitting by a higher desk or just taller people, Look out for Manufactures height extenders, or you could replace the ball with a bigger ball.