Our Primaloft® Lightweight socks utilize Primaloft® polyester yarn to keep your feet warm in a variety of temperatures, all without overheating or being excessively bulky.Primaloft® polyester yarn offers the best thermal performance to weight in a wide temperature range,Calf High - 18cm/7in with seamless toe construction,Fabric Content: 45% Polyester, 25% Polypropylene, 25% Polyamide, 5% Elastane.