https://en.wikipedia.org/wiki/Cuisenaire_rods
Cuisenaire rods are mathematics learning aids for students that provide an enactive, hands-on[1] way to explore mathematics and learn mathematical concepts, such as the four basic arithmetical operations, working with fractions and finding divisors.[2][3] In the early 1950s, Caleb Gattegno popularised this set of coloured number rods created by the Belgian primary school teacher Georges Cuisenaire (1891–1975), who called the rods réglettes.