The Mil-Spec Sport Sock shares specifications with U.S. Military socks: proven to promote moisture migration and support the foot's natural arch. These socks are tough. We made a slight change to the original "Mil-Spec" design, adding a compression band in the footbed for additional performance, comfort, and arch support. After giving this sock to some hard-wearers and saying, “do your thing," the results were better than expected. This sock stood up to heavy-use hiking, trail running, biking, and other outdoor activities.