REI Co-op Midweight Base Layer Half-Zip Top - Women's Black Heater Size XL Recycled polyester/spandex has a smooth face so layers slide on easily, and is peached for a supersoft next-to-skin layer Fabric wicks moisture and dries quickly to keep you comfortable Flatseam construction reduces bulk and chafing, and rolled-forward shoulder seams prevent abrasion from pack straps Thumbholes hold sleeves in place and help seal warmth in