1. Smooth, allowed for high speed playing, suitable for both children and adults. 2. Useful for practicing brain, memory and improve hands skills. 3. There is 15pcs in a set, you can combine different degree of difficulty kit. 4. Educational purpose and psychological purpose. 5. If the small metal ball falls into the holes of any side, you can lean forward the first side and shake it softly, then the ball comes out.
