The importance of an abacus is akin to that of a good musical instrument for a musician. Abacus is a multi-purpose tool. It does not need to be expensive, as long as it meets several requirements:
(1) the upper column has should have 1bead and the lower column should have 4 lower beads (the so-called 1-4 beads). The old abacus with two upper beads and five lower beads (2-5 beads) does not work.
(2) Abacus must be made out of wood. It should have 13~23 columns. Wooden abacus has higher quality and does not break easily. Its beads also do not stick.
(3) The beads should be small. Every bead should not be no wider than 12 millimeters. Abacus education is targeted toward children aged 6 to 10 who have smaller palms, and smaller beads make it easier for them to wield the abacus. Most importantly, as students progress and become more experienced, the image of abacus in their brain will be clearer and wider if the beads are small. This helps boosts mental arithmetic speed and accuracy.
Therefore, the choice of an abacus is the most important preparation of learning mental arithmetic.