Mixing the magic of merino wool with eco-conscious style, the Smartwool Classic All-Season Plant-based Dye Merino Base Layer is a next-to-skin option for us in spring, summer, fall, and winter. Merino wool is soft, insulates when wet, and naturally wicks moisture and resists odor, making it the perfect fiber to regulate our temperature in all conditions. The plant dye provides interesting styling that's also easier on the environment, making this an intriguing layering piece that looks good and feels good, too.