Measuring your head: Using a tape measure, measure the circumference of your head about 1/2" above your eyebrows. You may also use a string and then measure the string with a ruler. If you are between sizes go to the larger one

SIZE    INCHES                  CM

M       21 7/8 to 22 1/4        57Shelby      

M        22 5/8 to 23            59Oxford, Croyden, Malone

L          23                             58.5Shelby

L          23 1/2 to 23 7/8      59.5-60 Oxford, Croyden, Malone

XL        23 1/2                       59.5Shelby

XL        23 1/2 to 23 7/8       61      

M/L     21 3/4 to 22 3/4       57-59

L/XL    23 to 24                    59-61