Size guide
| Standard size Circumference in mm |
Diameter in mm | Diameter in inches | SP / IT | USs | UK |
| 44 | 14 | 10" | 4 | 3 | F 1/2 |
| 46 | 14.6 | 12" | 6 | 3 3/4 | H |
| 48 | 15.3 | 14" | 8 | 4 1/2 | I 1/2 |
| 50 | 15.9 | 16" | 10 | 5 1/4 | K |
| 52 | 16.5 | 18" | 12 | 6 | L 1/2 |
| 54 | 17.2 | 20" | 14 | 6 3/4 | N 1/2 |
| 56 | 17.8 | 22" | 16 | 7 1/2 | P |
| 58 | 18.4 | 24" | 18 | 8 1/4 | Q 1/2 |
| 60 | 19.1 | 26" | 20 | 9 | S |
| 62 | 19.7 | 28" | 22 | 10 | T 1/2 |