Size guide

NZ	US	EU	Internal Diameter (mm)
F	2.75	43.5	13.9
F 1/2	3	44	14.1
G	3.25	45	14.3
G 1/2	3.5	45.5	14.5
H	3.75	46	14.7
H 1/2	4	47	14.9
I	4.25	47.5	15.1
I 1/2	4.5	48	15.3
J	4.75	48.5	15.5
J 1/2	5	49	15.7
K	5.25	50	15.9
K 1/2	5.5	50.5	16.1
L	5.75	51	16.3
L 1/2	6	52	16.5
M	6.25	52.5	16.7
M 1/2	6.5	53	16.9
N	6.75	53.5	17.1
N 1/2	7	54	17.3
O	7.25	55	17.5
O 1/2	7.5	55.5	17.7
P	7.75	56	17.9
P 1/2	8	57	18.1
Q	8.25	57.5	18.3
Q 1/2	8.5	58	18.5
R	8.75	59	18.8
R 1/2	9	59.5	19
S	9.25	60	19.2
S 1/2	9.5	61	19.4
T	9.75	61.5	19.6
T 1/2	10	62	19.8
U	10.25	62.5	20
U 1/2	10.5	63	20.2
V	10.75	64	20.4
V 1/2	11	64.5	20.6
W	11.25	65	20.8
W 1/2	11.5	66	21
X	11.75	66.5	21.2
X 1/2	12	67	21.4
Y	12.25	67.5	21.6
Z	12.5	68	21.8
Z 1/2	12.75	69	22
Z+1	13.25	70.5	22.4
Z+2	13.5	71	22.6