Wool / silk and mesh polyester fibers maximize breathability and temperature control. * Ultra-lightweight sock frame provides your foot with a contoured, aerodynamic glove-like fit. * Achilles tendon pad protects against rubbing and chafing, while functioning as a heel lock. * 35% merino wool, 31% polyester, 19% nylon, 14% silk, 1% elastic. * Made in USA. Care: Machine wash with lukewarm water, inside out. Tumble dry low.