The new Fitsok ISW is a power-packed running sock built for roads and trail. Constructed with Isolwool®, the ISW utilizes 39% merino wool, 39% polypropylene, 20% nylon, and 2% spandex to deliver superior moisture movement and a great fit. Three pairs to a pack--a great value. P.S. You can wear it to work for a quick transition, or just to keep your feet dry during the winter commute.