U. S. and Canada	Diameter (Inches)	Britain	Japan	France	Germany	Switzerland
1	0.487	B	1	•	•	•
1 1/4	0.495	B 1/2	•	•	•	•
1 1/2	0.503	C	•	•	•	•
1 3/4	0.511	C 1/2	•	•	•	•
2	0.520	D	2	41 1/2	13 1/4	1 1/2
2 1/4	0.528	D 1/2	•	42 1/8	13 1/2	2 1/8
2 1/2	0.536	E	3	42 3/4	13 3/4	2 3/4
2 3/4	0.544	E 1/2	•	43 3/8	•	3 3/8
3	0.553	F	4	44	14	4
3 1/4	0.561	F 1/2	•	44 5/8	14 1/4	4 5/8
3 1/2	0.569	G	5	45 1/4	14 1/2	5 1/4
3 3/4	0.577	G 1/2	6	45 7/8	14 3/4	5 7/8
4	0.586	H	7	46 1/2	15	6 1/2
4 1/4	0.594	H 1/2	•	47 1/8	15 1/4	7 1/8
4 1/2	0.602	I	8	47 3/4	15 1/2	7 3/4
4 3/4	0.610	I 1/2	•	48 3/8	•	8 3/8
5	0.619	J	9	49	15 3/4	9
5 1/4	0.627	J 1/2	•	49 5/8	16	9 5/8
5 1/2	0.635	K	10	50 1/4	16 1/4	10 1/4
5 3/4	0.643	K 1/2	11	50 7/8	•	10 7/8
6	0.652	L	12	51 1/2	16 1/2	11 1/2
6 1/4	0.660	L 1/2	•	52 1/8	16 3/4	12 1/8
6 1/2	0.668	M	13	52 3/4	17	12 3/4
6 3/4	0.676	M 1/2	•	53 3/8	•	13 3/8
7	0.685	N	14	54	17 1/4	14
7 1/4	0.693	N 1/2	•	54 5/8	17 1/2	14 5/8
7 1/2	0.701	O	15	55 1/4	17 3/4	15 1/4
7 3/4	0.709	O 1/2	•	55 7/8	•	15 7/8
8	0.717	P	16	56 1/2	18	16 1/2
8 1/4	0.726	P 1/2	•	57 1/8	18 1/4	17 1/8
8 1/2	0.734	Q	17	57 3/4	18 1/2	17 3/4
8 3/4	0.742	Q 1/2	•	58 3/8	18 3/4	18 3/8
9	0.750	R	18	59	19	19
9 1/4	0.759	R 1/2	•	59 5/8	19 1/4	19 5/8
9 1/2	0.767	S	19	60 1/4	19 1/2	20 1/4
9 3/4	0.775	S 1/2	•	60 7/8	19 3/4	20 7/8
10	0.783	T	20	61 1/2	20	21 1/2
10 1/4	0.792	T 1/2	21	62 1/8	20 1/4	22 1/8
10 1/2	0.800	U	22	62 3/4	20 1/2	22 3/4
10 3/4	0.808	U 1/2	•	63 3/8	•	23 3/8
11	0.816	V	23	64	20 3/4	24
11 1/4	0.825	V 1/2	•	64 5/8	•	24 5/8
11 1/2	0.833	W	24	65 1/4	21	25 1/4
11 3/4	0.841	W 1/2	•	65 7/8	•	25 7/8
12	0.849	X	25	66 1/2	21 1/4	26 1/2
12 1/4	0.858	X 1/2	•	67 1/8	21 1/2	27 1/8
12 1/2	0.866	Y	26	67 3/4	21 3/4	27 3/4
12 3/4	0.874	Y 1/2	•	68 3/8	•	28 3/8
13	0.882	Z	27	69	22	29
U. S. and Canada	Diameter (Inches)	Britain	Japan	France	Germany	Switzerland