I purchased these from a handmade artist's website for a photoshoot of my 0-year-old and 6-year-old brothers, and they are in very good condition as they were only worn for photoshoots. The M size was a little small for my 6-year-old son (who has a large head). S size: Head circumference approx. 41cm, 0-1 year old M size: Head circumference approx. 44cm, 3-5 year old *Sizes are approximate. Please note that there may be some error due to amateur measurements. The hats are made of yarn and will stretch slightly.