Keep their feet comfortable with these cooling hiker socksFull cushion design with knit-in arch support32% cotton, 31% cooling polyester fiber, 18% nylon, 17% polyester, 2% elastaneTwo pairs per packageSize S fits toddler shoe size 9 to 11Size M fits toddler shoe size 12 to 13-1/2 and youth size 1 to 4-1/2Size L fits youth shoe size 5 to 8-1/2