About abacus, how to choose a suitable abacus

The best color of beads is brown. Black is generally OK, but white is the worst. It is best to choose a wooden abacus because it feels better to play and the size is the same. It is recommended for middle school students and above. For the larger one, choose the smaller one below. The smaller abacus is more suitable for two-finger dialing, and the larger one is more suitable for three-finger abacus.