Baby Knit Hat Acorn Hat Acrylic Yarn Washable Bi-color Set of 2 New, unused Set of 2, pink and green. How about matching hats for siblings? These hats were carefully and lovingly hand-knitted by a mom who is skilled at knitting. There are slight variations, but the size is for a head circumference of 46-50 cm. When laid flat, it measures 22 cm. In my son's case, he was able to wear it from 7 months old and can still wear it at 2 years old. The 2nd and 3rd photos are for image reference of them being worn. The 2nd photo shows a 1-year-old on the left and a 7-month-old on the right. The 3rd photo shows a 1.5-year-old child wearing it. (All sizes are the same.)