Use the chart to help you work out which size you need. If in doubt please contact a jeweller locally to help you in taking a précis measure. The mm marked in red is the stadard I use.
|
Size (inches)
|
Size
(mm)
|
Diameter (mm)
|
U.S.A. size
|
Japanese size
|
British size
|
German size
|
Swiss size
|
|
1 14/16
|
48
|
15.27
|
4 1/2
|
8
|
I – 1/2
|
15 1/4
|
—
|
|
1 15/16
|
49
|
15.70
|
5
|
9
|
J 1/2
|
15 3/4
|
—
|
|
2
|
51
|
16.10
|
5 1/2
|
11
|
L
|
16
|
11 3/4
|
|
2 1/16
|
52
|
16.51
|
6
|
12
|
M
|
16 1/2
|
12 3/4
|
|
2 2/16
|
53
|
16.92
|
6 1/2
|
13
|
N
|
17
|
14
|
|
2 3/16
|
55
|
17.35
|
7
|
14
|
O
|
17 1/4
|
15 1/4
|
|
2 4/16
|
56
|
17.75
|
7 1/2
|
15
|
P
|
17 3/4
|
16 1/2
|
|
2 5/16
|
57
|
18.19
|
8
|
16
|
Q
|
18
|
17 3/4
|
|
2 6/16
|
58
|
18.53
|
8 1/2
|
17
|
Q 1/2
|
18 1/2
|
—
|
|
2 7/16
|
59
|
18.89
|
9
|
18
|
R 1/2
|
19
|
—
|
|
2 8/16
|
61
|
19.41
|
9 1/2
|
19
|
S 1/2
|
19 1/2
|
—
|
|
2 9/16
|
62
|
19.84
|
10
|
20
|
T 1/2
|
20
|
—
|
|
2 10/16
|
63
|
20.20
|
10 1/2
|
22
|
U 1/2
|
20 1/4
|
—
|
|
2 11/16
|
65
|
20.68
|
11
|
23
|
V 1/2
|
20 3/4
|
—
|
|
2 12/16
|
66
|
21.08
|
11 1/2
|
24
|
W 1/2
|
21
|
—
|
|
2 13/16
|
68
|
21.49
|
12
|
25
|
Y
|
21 1/4
|
27 1/2
|
|
2 14/16
|
69
|
21.89
|
12 1/2
|
26
|
Z
|
21 3/4
|
28 3/4
|
|
2 15/16
|
70
|
22.33
|
13
|
27
|
—
|
22
|
—
|
|
