What Our Gearhead® Experts Are Saying:"I use the Performance Wool 1/2-Zip for everything from winter ski sessions to cool-weather runs. The merino-Tencel blend is magic—it breathes, wicks moisture, and regulates temperature without getting clammy. Mesh panels under the arms are a game-changer for airflow, and the flatlock seams make it comfortable even on multi-hour workouts."When we push our limits, the Performance Wool 1/2-Zip Top keeps pace. Blending 50% merino wool with 50% Tencel, it’s soft, lightweight, and designed to handle the extremes of high-intensity training. Whether we’re climbing in cold air or sprinting under a winter sun, the temperature-regulating fabric adapts to keep us comfortable and focused. Thoughtful details make it more than just a base layer. Integrated mesh panels at the back and underarms keep ventilation high, while flatlock seams reduce chafing during long sessions. The half-zip design lets us control airflow, and the slim fit layers effortlessly under shells or midlayers. From ski trails to early spring runs, this base layer is built for athletes who train year-round.