Ballo - Multipurpose Office Stool by Humanscale - Blue Eco-Friendly TPV Materials New, modern interpretation of the classic ball chair is designed by Don Chadwick - the designer of the Aeron Chair Spool shaped central column is made from strong, long-lasting polypropylene Air-filled, non-slip, dimpled domes shape to your body and provide a comfortable sitting experience Product Dimensions: 17.8"W x 24.5"H is easy to clean and durable