Busy Mom I bought this pool to fill up with 3" diameter plastic balls for an indoor ball pit to keep my very active 2 year old and 1 year old sons busy in the winter and early spring when the weather outside wasn't very kid friendly. They had a ball, literally! I love pulling this out for the kids to play with. This is the second year buying an inflatable pool for a ball pit but this one was GREAT since it had that 3rd RING and made it more durable and a deeper ball pit for the boys. Thanks Meijer!