The Ironman Flash Pro Sock boasts the patented UltiMax Pro moisture control system to keep your feet cool, dry, and blister-free. X2O acrylic absorbs moisture, provides superior insulation, and contains Chitosan (which has natural antimicrobial properties). The heel tab prevents the sock from slipping, while mesh air vents allow maximum breathability. The sock features a lightweight, breathable mesh instep; cushioned sole; seamless toe closure; and a comfortable, foot-hugging fit. 83% stretch nylon, 16% X2O acrylic, 1% spandex fabric blend. Made in the USA.