Rings all blues
| Milimetres | UK/Australia | US & Canada | France/Russia | Germany | Japan/India/China | Switzerland/Italy/Spain |
|---|---|---|---|---|---|---|
| 50 | K 1/2 | 5 1/2 | 50 1/4 | 10 | 10 1/4 | 10 1/4 |
| 52 | M | 6 1/4 | 52 1/8 | 16 3/4 | 12 | 12 1/8 |
| 54 | O | 7 | 54 | 17 1/4 | 14 | 14 |
| 56 | P 1/2 | 7 3/4 | 55 7/8 | 18 | - | 15 7/8 |
| 58 | R | 8 1/2 | 57 3/4 | 18 1/2 | 17 | 17 3/4 |
| 60 | - | 9 1/2 | 60 1/4 | 19 1/2 | 19 | 20 1/4 |
| 62 | U | 10 1/4 | 62 1/8 | 20 | 21 | 22 1/8 |
| 64 | V 1/2 | 11 | 64 | 20 3/4 | 23 | 24 |