4 years & up. Experience the fun and ingenuity of slippery spheres, silly squares, and jelly stones all in one convenient set. Simply add water and watch in amazement as they expand to as much as 200 times their size! Fun to bounce, roll, stack, and mix. They even slip, slide, and explode. Completely reusable, just dry them out and hydrate again and again. Environmentally friendly. Includes an informative guide. Trays are not included.