Smartwool Women's PhD Run Ultra Light Micro Sock Mesh,Nylon,Wool Made in USA Turn the heat up on the pavement, and not in your shoes, when you gear up for your next run with the Smartwool&reg; PhD&reg; Run Ultra Light Micro running sock! Sold as a single-pair pack. Micro sock sits below the ankle. Ultralight cushioning for optimal next-to-foot comfort without the added bulk. 4 DEGREE&trade; Elite Fit System employs two elastics for greater stretch and recovery. ReliaWool&reg; technology delivers long lasting wear. 200 needle construction provides the highest knit density without compromising it ultralight weight. Strategically-placed mesh vents for temperature and moisture management. Achilles tab helps reduce the likelihood of irritation. Run-specific fit. 48% wool, 48% nylon, 4% elastane. Machine wash inside out on a warm, gentle cycle. Tumble dry low, lay flat