Our THICKEST, loftiest, most comfortable sock: Versatile Hollow boot socks are the perfect fit for facing the bitter cold, or warming up post-outdoor adventure. Fabric Content: Our boot performance socks use 70% Premium Peruvian Baby Alpaca Fiber, 27% Nylon and 3% Spandex to deliver the same comfort and performance as our flagship crew sock, but every aspect is extra. Care recommendation: Wash cold, hang dry - (note: machine washing and drying tests have shown no damage). Made in USA: Designed in Wisconsin by outdoor enthusiasts and made in North Carolina.