I'm on my second one, and the ball still wont' stay inflated.  The first one we received didn't have a rubber stopper in the inflation hole, so that was defective.  The replacement one we received looked O.K. but when inflated you can hear the air coming out of the same inflation area.  We double checked the directions to see if there was some secret step we missed but bottom line the ball was defective and won't stay inflated.  I'm sending both units back - very frustrating for 8 year old who's been waiting by the door everyday for her tetherball set to arrive.