Time To Run Performance Coolmax Running Sock Pack Of Two Lycra ankle cuff contains excellent stretch properties to help prevent the sock sliding down. Terry pad provides protection against both impact and abrasion. Y Heel construction-provides a better fit for optimum comfort and performance. Support zone containing lycra which helps the sock to remain in place and giving a firm, supportive fit around the arch of the foot. A flat toe seam to help prevent blisters.