Ultra-lightweight and quick-drying ArmourDry technology improves performance. It disperses moisture evenly, allowing sweat to evaporate faster for a lighter, drier, cooler run. Breathable mesh ventilation ducts where it's needed most. Energy Return cushioning on the heel and toe for more protection in high-impact areas without more bulk. The Locked-in Fit construction keeps the sock securely on the heel, so it doesn't need to be adjusted and won't fall down. Built-in arch support. Anti-odor technology reduces odor in the sock. The seamless toe box provides excellent comfort and reduces irritation.