Build strength by using this 13-1/2" diameter air-filled disc when doing balance-based exercises. Enhance balance and functional training by incorporating 2 discs. The bottom of the VersaDisc has small nodules for use in rehabilitation and massage therapy; also keeps disc from moving during exercise. Soft PVC. 13-1/2" diam. x 3" H. 3 lbs. Ships inflated however some users may need to adjust the inflation level; maximum inflation is 4" high. Inflation instructions included. Sold individually.