Smartwool Men's Classic Thermal Merino Boxed Long Sleeve Base Layer Shirt - The Smartwool Classic Thermal Merino Colorblock Base Layer is designed for comfort and performance in cool-to-cold temperatures. Flatlock seam construction minimizes chafing, while shoulder panels eliminate top shoulder seams. Made from 100% Merino wool, the fabric provides enhanced breathability, thermoregulation, and odor resistance. With a Classic Thermal temperature rating for use in conditions 50°F and below, this base layer keeps you warm and dry during your cold weather activities. Flatlock seam construction designed to minimize chafing Shoulder panels eliminate top shoulder seams 100% Merino wool fabric for enhanced comfort, breathability, thermoregulation,and odor resistance Temperature rating: classic thermal (Cool to Cold 50° F and below) Weight: 280g Fit: slim Style: SW016350K66