Size chart

US Size

 Inside Diameter

Inside Circumference

Australia + UK

Pandora

5

15.6mm

49.3mm

J 1/2

50

6

16.45mm

51.9mm

M

52

7

17.3mm

54.4mm

O

54

8

18.2mm

57.0mm

Q

56

9

19.0mm

59.5mm

R 1/2

58

10

19.84mm

62.0mm

T 1/2

60