Bobbi Spandex Fabric Office Ball Chair 17.75" D x 17.75" W x 19" H Upholstered with purple spandex fabric over rubber ball. Stands on black iron legs Great for balance improvement, spine alignment and posture. Strengthens core muscles Suitable for the office, or other periods that require sitting for long duration Many people have substituted the basic office chair for the ball chair to improve overall health. The round structure of the ball chair improves spine alignment and balance for better posture and even works the core muscles. The Bobbi ball chair is a great option when sitting long hours like at the office and the bright and fun color is an added bonus, plus the spandex fabric will keep you from slipping.