Fitsok ISW Trail Cuff Technical Socks (3-Pack) 39% Merino Wool, 39% Polypropylene, 20% Nylon, 2% Spandex Made in US The ISW utilizes merino wood and polypropylene to deliver superior moisture movement A light cushion prevents blistering and enables prolonged performance in the harshest conditions Innovative technology promotes airflow on all sides of the foot, dispersing heat and moisture around the foot