REPREVE Recycled Materials - Moisture-wicking to keep feet feeling fresh and dry in intense workout pressure. Top Vents - Allows constant airflow to keep feet and toes cool and fresh. HeelPower - Keeps the heel stable and secure, preventing the socks from slipping around in the socks. Arch Bracing - Adds support and stops the socks from slipping around. Materials - 65% REPREVE Nylon / 34% Polyamide / 2% Elastane.