Description Klim Aggressor Sock 3.0 Teton Merino Wool blended w/ acrylic, Polyamide Nylon, Lycra, SoftAir Polyester for durability & comfort (36% Merino Wool, 31% Acrylic, 12% Nylon, 17% Elastane, 4% Polyester) Made of European sourced yarns Reinforced toe, heel, sole Full Terry Loop construction for cushioning and warmth Arch & ankle support stretch bands Patterned front mid ankle bend for reduced bulk Tubular cuff for better fit & stretch recovery Over-the-calf height SM = 4-6, MD = 7-9, LG = 10-12, XL = 13-15