Smartwool Women's Phd&reg; Ski Light Performance Socks, Black, Large New 4 Degree Elite Fit System uses two elastics for greater stretch and recovery to keep the sock in place Patent pending ReliaWool Technology in high impact areas provides the longer lasting protection to keep feet comfortable Strategically placed mesh ventilation zones provide ventilation for temperature and moisture management Flat knit durable toe seam for high burst strength Knit in USA of 67% Merino Wool, 31% Nylon, 2% Elastane