In savage summer heat Darn Tough's Vertex Running Series socks made with Coolmax® are designed to keep their cool. Coolmax® Polyester yarns are engineered to move moisture away from your skin and be fast drying. Combine that with a sock that weighs in at a mere 13 grams and you have the ultimate warm weather running companion. True Seamless construction reduces hotspots and blisters. Ultra high stitch count creates a super comfortable sock with a streamlined fit like no other. No slipping, no bunching, no blisters. Plus they even have that handy lil’ tab on the back so they slip on easy. Still made in Vermont. Guaranteed for life.