The Steigen Running Sock is an extra-thin, extra-lightweight sock that reduces heat, friction and sweat to prevent blisters. They're designed to feel like you're not wearing socks at all. Fits sizes 5-12 US. Steigen running socks feature: Lightweight fabric for fast moisture transfer and breathability, with Airflow top mesh and microfiber nylon/lycra body for a tight fit Forefoot pad for extra comfort and durability Super flat toe seam to eliminate chafing Y-shaped heel that prevents bunching inside your shoes Ankle-crease reduction channels Arch supports.