Perfect for indoor or outdoor play, these heavy-duty blocks will create solid pathways for children to walk upon, tunnels for them to crawl through, or even a playroom to call their own. Because each block is exactly a square foot, they can be used for simple activities that introduce linear and area measurement. Each set includes square blocks, both solid and see-through, plus triangular blocks for pathway corners and pointed rooftops. Ages 1 1/2-5.