The low one is for the child who has just learned to sit. The big one is for the older child, and once you stack them, they fit teenagers and grown-ups. It is nice to have an example of each animal, because the child grows along with them, and as a result they can be used over a long period of time. You can roll the animal to one another, or roll and chase it. The 3-layer version of the Fish is a seat for the small child – and later they can stand on it to take steps up/down from it, which enhance strength, balance and coordination. The 3-layer version is superb as a step stool in the bathroom, since it does not slide on the wet floor. The size and material makes it so light that the child can lift the tumbling animal themselves.