The Small is for those with shorter hair and a smaller head circumference.
The Medium (average head size) is perfect for all styles when the hair is short or straightened.
The Large has more material in the scarf and fits nicely when wearing a large curly ponytail, curly wig, long braids or any style with a lot of hair.
***The Medium can be worn with larger hair styles but will not afford you enough fabric if you like the longer tail and different tying techniques and versatility.
***Be warned, if you do have a smaller head.. the Large will probably be too large for you as the Visor may not fit as snug against your temples as it should and will compromise the look of the product.