The Clima-Wool construction features a resilient merino wool, nylon, and spandex combination, perfect for outdoor activities in both warm and cold environments. This fabric is designed to deliver top-notch performance and coziness regardless of season. Clima-Wool fabrics feature incredible breathability and temperature control for a comfy fit in any environment. The Women's Merino zip-t base layer is fast-drying and sweat-wicking, allowing you to remain dry and energized no matter the activity.