Unique inflatable ball has stabilizing "feet" that keep the ball from rolling when not in use. When in use the weight of the person makes the "feet" retract into the ball so it can function like any other inflatable exercise ball. Non-slip surface is ribbed for extra security. ?Under" inflate to give a soft, mushy feel or fully inflate for a firm, bouncy feel. Ball can support up to 300 pounds. Comes in a polybag. Available in various color-coded sizes.