Smartwool M CLASSIC THERMAL MERINO BL COLORBLCK CB Men's undershirt: The Smartwool M CLASSIC THERMAL MERINO BL COLORBLCK CB is made from carefully sourced 100% Merino wool. The heavier Merino 250 material is ideal for cold weather activities where warmth and breathability are essential. It provides breathability, thermoregulation and odour resistance, is moisture wicking and antibacterial. Thanks to the shoulder panels and flat seams, this base layer brings maximum comfort, is pleasantly warm and can be relied on for winter hiking, running and skiing. Smartwool M CLASSIC THERMAL MERINO BL COLORBLCK CB