Exclusive Thor-Lon and natural wool construction to deliver superior insulation, softness, durability moisture wicking for warmer, drier, better feeling feet Fibers are chosen for performance and durability resulting in a sock that wears for years Unique Thorlo padding designed for cold weather boots Padding is clinically shown to reduce blisters, moisture, pain, and pressure Cushioned instep and arch for a better fit, more support, and less pressure on your feet Ventilation panel for extra moisture control and breathability Low profile toe seam won't rub or irritate feet Named a "Guides Choice" by the American Alpine Institute