SOS Socks standard design is anything but standard. They use core-spun COOLMAX fabric which is the best of both worlds; unsurpassed moisture management and LYCRA; sport stability. SOS' specific knitting machines place the COOLMAX fabric on the inside of the socks where it controls moisture from the foot; while the 3-ply nylon is used on the outside of the sock for strength and durability. The core-spun yarn is the most efficient way of knitting LYCRA; fabric into the foot of the sock and still allow both the COOLMAX fabric and nylon to be sandwiched together. The cool designs are just a disguise; it's a unique construction of the best materials and is unmatched anywhere. Made in USA.