SMALL Fits

Women's shoe sizes 5-1/2 to 10
Men's shoe sizes 3-1/2 to 7

MEDIUM Fits

Women's shoe sizes 11 and up
Men's shoe sizes 7-1/2 to 14

99% of women wear size small, and 99% of men wear medium. If you are a borderline size or have narrow feet, then we recommend starting out with the Small size.