size guide

Measure	Circumference cm	Diameter cm
8	1.53	4.8
9	1.56	4.9
10	1.6	5.02
11	1.62	5.09
12	1.65	5.18
13	1.68	5.28
14	1.72	5.4
15	1.74	5.46
16	1.78	5.59
17	1.81	5.68
18	1.85	5.81
19	1.88	5.9
20	1.92	6.03
21	1.95	6.12
22	1.98	6.22
23	2	6.28
24	2.04	6.41
25	2.06	6.47
26	2.1	6.59
27	2.12	6.66
28	2.15	6.75
29	2.19	6.88
30	2.22	6.97
31	2.25	7.07
32	2.29	7.19
33	2.33	7.32