The Chinese version of the abacus, called a Suan Pan, has 7 beads per rod. Each rod of the Suan Pan can represent a digit from 0 to 15. In ancient China they used a base-16 numbering system. The Suan Pan can also be used to do calculations on base 10 numbers but has the additional complexity of the two additional beads per rod. The Russian version of the abacus, called a Schoty, has 10 beads per rod. The Russian abacus has horizontal rods while the Japanese or Chinese abacus have vertical rods. An abacus can have any number of rods typically an odd number such as 15, 17, 31, 33 rods