Size Chart The PhD(R) Outdoor Light Micro Socks feature ReliaWool(TM) technology for improved durability in the heel and toe. Smartwool's 4 Degree(TM) elite fit system keeps the sock in place and give you all-sport versatility. Versatile light cushioning makes them perfect for varied trail and road terrain. Features: - Strategically placed mesh ventilation zones provide ventilation for temperature and moisture management - Flat knit durable toe seam - Achilles pad - 1.75" overall height - Sock Height: Micro - Knit in USA of Imported Yarn: 66% Merino Wool, 32% Nylon, 2% Elastane - Last Chance: Discontinued Style - Only available to ship within the USA