ECR4Kids Tunnel and Arch Set, Ages 4 And Above, Set of 10 Pieces ECR4Kids Tunnels and Arches Set is suitable for kids who think outside the box and helps to improve architectural skills. It has curved blocks that are perfect for constructing tunnels, bridges or the loch ness monster. 10-Birch block set comes with four different widths and perfect for use in the classroom or at home. Ages 4 and above.