Size Small = Wrist Circumference of 5 inches or less (Children and petite
wrists)
Size Medium = Wrist Circumference between 5 to 7
inches (Fits most teens and adults)
Size Large = Wrist Circumference over 7 inches (Fits large adults)
If
you are unsure of what size you need, first try size Medium.....it fits
75% of peoples' wrists.