FARO
Small:
Oval Head Shape: 52cm - 55cm | 20.5in - 21.7in
Round Head Shape: 52cm - 54cm | 20.5in - 21.3in
Medium:
Oval Head Shape: 55cm - 59.5cm | 21.7in - 23.4in
Round Head Shape: 54cm - 58cm | 21.3in - 22.8in
Large:
Oval Head Shape: 59.5cm - 62cm | 23.4in - 24.4in
Round Head Shape: 58cm - 60.5cm | 22.8in - 23.8in
When in doubt between Small & Medium or Medium & Large, always opt for Medium.