These Fox River Liners use polypropylene moisture mover to keep your feet dry by moving moisture away from your feet and into your socks. Liners reduce friction and are a great solution for those prone to blisters and hot spots. Ultra lightweight fabric means these will easily fit in your favorite socks. Fox River socks are guaranteed against manufacturing defects for 1 year and are proudly made in America. Specs: 93% polypropylene, 6% nylon, 1% spandex