Anyone who spends a lot time outdoors in the winter knows a good base layer is crucial for comfort in cold weather. This high-performance fabric* not only traps your body’s heat but actually generates heat by absorbing body moisture. It also wicks perspiration away from your skin to the outer surface of the garment so you stay dry underneath. Our Midweight ThermaskinTM Heat Half-zip also has plenty of give to keep up with active pursuits. *Heat technology is guaranteed for approximately 30 washes. 100% polyester. Machine wash. Imported.