The ultimate fusion of superb fit and maximum protection with minimal weight, the PhD Running Ultra Light Micro socks help you go the distance without weighing you down. 73% merino wool, 24% nylon, 3% elastic. SmartWool delivers itch free comfort, even foot temperature, moisture management, and odor control. WOW wool on wool Technology micro loop cushioning in the high density impact zones for protection and added durability under the heel and forefoot, around toes. 4 Degree Fit System banded compression at ankle, arch, lower and upper instep with flex zones provides high performance and all day fit. Strategic mesh zones for maximum ventilation MVT open mesh knitting pattern. Rib welt with achilles pad offers protection and holds sock up and in place. Duroyarn reinforcement for added comfort and durability. Flat knit toe seam for comfort and durability. Machine wash and dry shrink free.