The Swiftwick Aspire Seven Socks are knit in Tennessee of Olefin yarns. Olefin is a lightweight polypropylene fiber that wicks moisture to keep your feet dry. Dry feet mean less chafing and blisters. Additionally, the Olefin is hydrophobic so that it won't absorb moisture from the outside. The footbed is cushioned and conforms to the shape of your arch with a knit-in nylon and spandex arch support. This thicker knit gradually becomes a channeled upper that acts as a subtle compression sock, helping to improve blood flow through your extremities.