Wacces Balance Disc is a space-saving alternative disk to a therapy ball and/or sitting wedge. One try, and you"ll be addicted to its feel, benefits and uses. Wacces Balance Disc promotes an upright posture, improves balance, exercises trunk musculature, and integrates vestibular responses and tilting reactions. Ideal for clinic or a send-home therapy tool. Features a 13 inch (33cm) diameter. Color may vary.The Wacces 13" balance disc is our most economical and versatile balance trainer and seating cushion. It"s very portable. Since the air is shifting within the disc the user recruits stabilizing muscles whether seated or standing. The user is constantly presented with a slightly changing and ever unstable surface. Learning to react, recover and find balance equilibrium is the goal of balance training. This balance disc is also used in day care centers for floor seating, at the office for seat cushioning and core ab and back stimulation, by hunters looking for a portable ground cushion, by sports fans as a portable stadium seat cushion and at home in the kid"s play room.