Fit & Design: Performance Fit: No slipping, no bunching, and no blisters Fine Gauge Knitting: Unprecedented durability and our unique "put it on, forget it's on" feel Fast Action Wicking: Pulls moisture away from skin. Fast drying All Weather Performance: Cool in the summer, warm in the winter Merino Wool is fast drying, breathable and odor resistant for all-day comfort Additional Details: Guaranteed For Life: No strings. No conditions. For life. Cushion in the Hike/Trek category features terry loops under the foot, and in the taller styles reaches above the ankle for comfort and protection