Drymax® Sports Socks have many unique characteristics, but the main feature is the NEW fiber called Drymax®. Drymax® is super-hydrophobic (repels moisture); therefore we use it to line the inside foot area of our sock. Drymax® actually removes moisture from the inside to the outside of the sock. Sensura polyester is used on the outside because it attracts moisture and holds it away from the foot. This clever utilization of Drymax® on the inside and Sensura polyester on the outside truly keeps your feet dry!