Gauge or bore sizes.

1b 1.669 in (42.4 mm)
2b 1.325 in (33.7 mm)
3b 1.157 in (29.4 mm)

4b 1.052 in (26.7 mm)

5b .976 in (24.8 mm)
6b .919 in (23.3 mm)
7b .873 in (22.2 mm)

8b .835 in (21.2 mm)

9b .803 in (20.4 mm)

10b .775 in (19.7 mm)

11b .751 in (19.1 mm)

12b .729 in (18.5 mm)

13b .710 in (18.0 mm)
14b .693 in (17.6 mm)
15b .677 in (17.2 mm)

16b .662 in (16.8 mm)

17b .649 in (16.5 mm)
18b .637 in (16.2 mm)
19b .626 in (15.9 mm)

20b .615 in (15.6 mm)

21b .605 in (15.4 mm)
22b .596 in (15.1 mm)
23b .587 in (14.9 mm)

24b .579 in (14.7 mm)

25b .571 in (14.5 mm)
26b .563 in (14.3 mm)
27b .556 in (14.1 mm)

28b .550 in (14.0 mm)

29b .543 in (13.8 mm)
30b .537 in (13.6 mm)
31b .531 in (13.5 mm)
32b .526 in (13.4 mm)
33b .520 in (13.2 mm)
34b .515 in (13.1 mm)
35b .510 in (13.0 mm)
36b .506 in (12.9 mm)
37b .501 in (12.7 mm)
38b .497 in (12.6 mm)
39b .492 in (12.5 mm)
40b .488 in (12.4 mm)
41b .484 in (12.3 mm)
42b .480 in (12.2 mm)
43b .476 in (12.1 mm)
44b .473 in (12.0 mm)
45b .469 in (11.9 mm)
46b .466 in (11.8 mm)
47b .463 in (11.8 mm)
48b .459 in (11.7 mm)
49b .456 in (11.6 mm)
50b .453 in (11.5 mm)

.67b .410 in (10.4 mm)