Merino wool has long been heralded as nature's best temperature-regulating fabric. With the ability to hold onto heat in cold temps, manage moisture in humidity or during strenuous activity, and dry quickly in any type of wet environment, there's no doubt as to why we choose merino wool for one of our most important layers: the foundation. For chilly backpacking, mountaineering, or skiing trips, and for humid hiking, paddling, and climbing excursions, the Alpine Onset Collection are the base layers you need to keep your temperature in check. Using 83% merino wool with a touch of nylon and spandex for extra mobility, each Alpine Onset piece features a trim fit as your next-to-skin layer for easy layering and efficient temperature control. A flat seam construction prevents chafing, and a lightweight, compact design makes it easy to fit an extra layer or two in your pack. Plus, merino wool naturally blocks odors - making it an easy winner that both you and your tentmate will appreciate. Fabric: 83% merino wool, 12% nylon, 5% spandex. Weight: 1.2 oz/33 g. Breathable. Wicking. Anti-Odor. Windproof. Water Resistant. Breathable. Mesh Breathing port. Flat-Seam Construction. Helmet Compatible. Machine wash. Imported.