Heat Holders Thermal Socks Childrens Older Navy. Heat Holders® socks for children are available in two sizes, both in array of lively colors! The Younger Children's style is children's size 10 - 2½, for children aged approximately 3 to 8 years old. The Older Children's style is children's size 3 - 6½, for children aged approximately 8+ years. Both styles are in a long length. Choose a style to buy now! Tights for girls ages 7-13 also available. All styles available in multiple colors!.