We do have sized categories such as S, M, L, XL, please see the following as the guide:
S: 8cm x 8cm or less
M:13cm x 13cm or less
L: 17cm x 17cm or less
XL: Anything from 20 - 30cm
S: 8cm x 8cm or less
M:13cm x 13cm or less
L: 17cm x 17cm or less
XL: Anything from 20 - 30cm