What Size to Choose? Itty-Bitty= perfect for those younger than 3-5 months old. Made to fit snugly for safety. Child (infant)= for ages 6 months to 2 years old. Average head circumference 16-18cm. Small Child (3-10 yrs old)= Average head circumference 20cm. Comes with adjustable drawstring (majority styles). If child has long hair or for long braids/hairstyles, please order adult size. Big kid/Adult (11yrs+)= Large size. This size is the same as the adult size bonnet. Comes with adjustable drawstring (majority styles).