These are Seikatsukon socks. I purchased them from Marmer Books and Socks, and they are a special order color. They are meant to be worn as the outermost layer of layered socks. They are cotton 100% toe-round high socks. They are made of natural materials and are knitted with a special method that doesn't constrict. They are really useful when you're wearing a dress or skirt and your feet are cold, and they make your feet look cute and neat! The M size has a moderate fit, and the L size gives a generous high-sock feel! China Blue is a light navy color. Cotton 100% Color: China Blue Size: L (up to about 27cm)