NZ, Australia, UK	USA, Canada	Asia	Europe	Inside Diameter (mm)
A	½	–	–	12.04
A ½	¾	–	–	12.24
B	1	1	–	12.37
B ½	1 ¼	–	–	12.65
C	1 ½	–	–	12.85
C ½	1 ¾	–	–	13.06
D	2	2	1 ½	13.26
D ½	2 ¼	–	–	13.46
E	2 ½	3	2 ¾	13.66
E ½	2 ¾	–	–	13.87
F	3	4	3	14.07
F ½	3 1/8	–	–	14.17
G	3 3/8	5	5 ¼	14.38
G ½	3 5/8	6	–	14.58
H	3 ¾	–	6 ½	14.68
H ½	4	7	–	14.88
I	4 ¼	–	7 ¾	15.09
I ½	4 ½	8	–	15.29
J	4 5/8	–	9	15.39
J ½	5	9	–	15.7
K	5 1/8	–	10	15.8
L	5 ½	–	11 ¾	16.1
L ½	5 7/8	–	–	16.41
M	6	12	12 ¾	16.51
M ½	6 ¼	–	–	16.71
N	6 ½	13	14	16.92
N ½	6 ¾	–	–	17.12
O	7	14	15 ¼	17.32
O ½	7 ¼	–	–	17.53
P	7 ½	15	16 ½	17.73
P ½	7 ¾	–	–	17.93
Q	8	16	17 ¾	18.13
Q ½	8 ¼	–	–	18.34
R	8 5/8	–	19	18.64
R ½	8 7/8	–	–	18.85
S	9 1/8	–	20 ¼	19.05
S ½	9 3/8	–	–	19.25
T	9 5/8	–	21 ½	19.46
T ½	10	20	–	19.76
U	10 ¼	21	22 ¾	19.96
U ½	10 ½	22	–	20.17
V	10 5/8	–	23 ¾	20.27
V ½	11	23	–	20.57
W	11 1/8	–	25	20.67
W ½	11 3/8	–	–	20.88
X	11 5/8	–	26 ¼	21.08
X ½	11 7/8	–	–	21.28
Y	12	25	27 ½	21.39
Y ½	12 ¼	–	–	21.59
Z	12 ½	26	28 ¾	21.79
Z ½	12 ¾	–	–	22