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 50degF 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 50deg F and below) Weight: 280g Fit: slim Style: SW016350001