Smartwool phd outdoor heavy otc socks features reliawool technology for improved durability in the high wear areas and the 4 degree elite fit system, to keep the sock in place and give you all-sport versatility. it is knit in usa of imported yarn. care instruction: machine wash warm gentle cycle and turn inside out before washing. do not bleach as it damages the natural wool fibre. tumble dry low, lay flat or line dry for best appearance. do not iron and dry clean.