BodySport Balance Disc is a 13.8 in. (35 cm.) in diameter inflatable blue disc that can be used as a dynamic cushion to activate major muscle groups, or as a standing disc for balance training and lower extremity strengthening. It is similar in shape and movement to that of a fitness ball when used on any seat. It features one tactile side and one smooth side and is easily inflated with a standard pump. It can either be deflated to a 1 in. thickness or inflated to a 2 in. thickness.