Work on your posture, balance and core strength while sitting in your favorite chair with the FitBALL Seating Disc Jr. from Ball Dynamics. The Seating Disc Jr. is a smaller 12in version of the FitBALL Seating Disc. This inflatable disc provides many of the benefits of an exercise ball and forces you to engage your core muscles while seated. This small seating disc is great for a home or office chair. The FitBALL Seating Disc Jr. can also be used as a balance disc while working out. Use it when doing push-ups or sit-ups for increased muscle training.