Heats the bottom of your feet80% heavyweight cotton and 20% spandexGreat for skiers, snow boarders, snowmobilers or for those extremely cold daysRequires 2 AA batteries per sock, 4 batteries in total (sold separately)Removable battery box with on and off switchSizes: Small (fits men’s shoe sizes 5-9), Medium (fits men’s shoe sizes 9-11.5), Large (fits men’s shoe sizes 12-15)