Turn almost any chair or seat into an active one by placing the disc on top to add instability and strengthen your core. This posture-improving inflatable 16" Balance Disc will engage your abs and core muscles while you sit. Great for a meditation seat or wherever you need a little extra cushion. By controlling the firmness of the cushion, you can adapt it to your fitness needs and comfort-ability. Can also be used for strengthening exercises in or out of your chair.