English: The type of a carbon nanotube is described by two integers (n,m) that represent vectors n*u + m*v on the hexagonal (graphene) lattice between two atoms of the same parity (with bonds in the same direction). This picture shows all types (n,m) that define non-isomorphic nanotubes (the vectors from the leftmost red dot to the other red dots). The types (n.m) with 0 < m < n are chiral; their mirror images (m.n) are shown by the blue dots. A few of the vectors are drawn and labeled for illustration purposes.