We work with the British system which uses a letter system for ring sizing.
In the table below they are grouped to help understand better.
 
                                        WOMEN’S SIZES                                         
X-Small (G, G½, H, H½, I, I½)
Small (J, J½, K, K½, L, L½)
Medium (M, M½, N, N½, O, O½)
Large (P, P½, Q, Q½)
X-Large (R, R½, S, S½, T
 
MEN’S SIZES
Small (O, O½, P, P½, Q, Q½)
Medium (R, R½, S, S½, T, T½)
Large (U, U½, V, V½, W, W½)
X-Large (X, X½, Y, Y½, Z, Z½)