Made with 75% Ultra-wicking Micro Denier Acrylic 15% Nylon and 10% Spandex for exceptional comfort and strength. ALL of our socks feature our Stretch-to-Fit sizing system and our exclusive Easy-fit cuff for a PERFECT FIT every time on any foot. These features create superior softness and comfort and help eliminate blisters and hot spots. We also feature a double stitched heel & toe for added strength and durability. We deliver Superior Quality and High-Tech Comfort in every SockGuy sock we make. We guarantee it. Sizing: S/M: Men s 5-9 Women s 6-10 Euro 37-42 M/L: Men s 9-13 Women s 10-14 Euro 43-48