This 15-digit soroban abacus features a 1:4 bead layout (one bead worth 5 on the top deck, and four beads each worth 1 on the bottom deck. The orange plastic beads are laid on top of a black velvet background, which holds them firmly in place. The abacus is 6-3/8" x 3-5/8" and comes with a white plastic case (7-3/4" x 4").
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