| Size No. | Imperial Size Range | Metric Size Range |
|---|---|---|
| No.1 | 1/8" ~ 1/4" | M3 – M6 |
| No.2 | 1/4" ~ 5/16" | M6 – M8 |
| No.3 | 5/16" ~ 7/16" | M8 – M11 |
| No.4 | 7/16" ~ 9/16" | M11 – M14 |
| No.5 | 9/16" ~ 3/4" | M14 – M18 |
| No.6 | 3/4" ~ 1" | M18 – M25 |
| No.7 | 1" ~ 1-3/8" | M25 – M33 |
| No.8 | 1-3/8" ~ 2" | M33 – M50 |