The Outdoor Sport Ultra-Light Micro Sock features SmartWool's 4-Degree Fit System, which secures the sock in place for exceptional performance and fit. The reinforced heel and toe provide enhanced durability for long-lasting wear. The 1 x 1 ribbed welt and flat-knit toe seam help keep feet comfortable throughout the day. This ultra-light, non-cushioned micro sock is made from a rugged blend of 59% New Zealand Zque Merino wool, 39% nylon, and 2% elastane fabric. Made in the USA.