This abacus is perfect for helping kids learn about place value and our base 10 number system. The plastic set has 75 coloured cubes, 5 rods/links and numeral cards (139pieces in all). One link on its own is for the Units. Add a link for Tens + Units (for numbers up to 19). Add a link for Hundreds (for numbers up to 999). Add a link for Thousands (for numbers up to 9999). Lastly, all 5 links caters for numbers up to 99,999. When kids are ready, I actually have two sets (yes, further links can be added) to cater for much larger numbers up to 1,000,000 or more.