Klim Aggressor Sock 1.0. Teton Merino Wool blended with acrylic, polyamide nylon, Lycra for durability and comfort (30% merino wool, 30% acrylic, 25% nylon, 15% elastane). Made of European sourced yarns. Reinforced toe, heel, sole. Engineered Terry Loop for strategic cushioning and warmth. Arch and ankle support stretch bands. Arch and shin air channels for moisture control. Patterned front mid ankle bend for reduced bulk. Tubular cuff for better fit and stretch recovery. Over-the-calf height. Balanced temp control for wide range of conditions. Merino wool moisture-absorbing, warming, quick-dry, anti-odor properties. Designed for riding and riding boots. Sizing: SM = 4 - 6. MD = 7 - 9. LG = 10 - 12. XL = 13 - 15.