I bought these socks for my 4.5 years old son, and they kept his feet warm while in the snow. They are quite thick, and very comfortable. I think their sizes are a bit small, so you may need to order a larger size than your child's shoe size. My son wears 11.5 size shoes, and I ordered for him the Medium size socks. They were slightly big, but since they may shrink in the laundry, I think it was the right size for him.