Turn 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. Even works outdoors for a quick seat or on hardwood or carpet flooring. 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 comfortability. Can also be used for strengthening exercises in or out of your chair