The Minus 40° C Silver Crew Sock pairs perfectly with boots for ultimate warmth and comfort in extremely cold conditions. The sock is made from a super-soft blend of 75% merino wool, 15% stretch nylon, 7% olefin, 2% stretch polyester, and 1% elastic (rubber) fabric. A Smart Silver antimicrobial treatment works to kill germs and control odors, so feet stay fresh and fungus-free permanently. The sock features a fully cushioned sole; fortified foot bottom for long-lasting wear; seamless toe closure; and a comfortable, foot-hugging fit. Made in the USA.