The circles are glued into place, so it has only the 10 pieces to fit in the central tray. Despite the 231 solutions, it is very tough to find even one. Some of the pieces are fragile, so not recommended for younger children.
- red alder and black walnut wood
- 17 pieces
- unknown number of solutions
- 4″ x 4″ (10cm x 10cm)
- difficulty level: 9 out of 10