Smartwool Kids Wintersport Feather Socks wool 3x1 rib welt, medium full cushion leg & sole, flat knit toe seam SmartWool inside for moisture, temperature, and odor control. Flat knit toe seam. Over the calf height, medium cushion. 58% merino wool, 40% nylon, 2% elastane, washing machine and dryer friendly! Kid's Size XS=shoe size 6-8.5, S-shoe size 9-11.5, M=shoe size 12-2.5, L=shoe size 3-7