IN * MM * MM ** US & CA AU, NZ, UK & IE Etc
1 5/16 49 15.7 5 J 1/2 1
2 1/16 52 16.5 6 M 2
2 3/16 55 17.4 7 O 3
2 5/16 57 18.2 8 Q 4
2 7/16 59 18.9 9 R 1/2 5
2 9/16 62 19.8 10 T 1/2 6