US Size  Inside Diameter Inside Circumference UK Size
4 14.88mm 46.8mm H
5 15.70mm 49.3mm ½
6 16.51mm 51.9mm ½
7 17.32mm 54.4mm ½
8 18.14mm 57.0mm ½
9 18.95mm 59.5mm R ½
10 19.76mm 62.1mm T ½
11 20.57mm 64.6mm V ½