The Smartwool Classic Thermal Merino Base Layer 1/4 Zip Top is a big time baselayer for environments that make the mercury shiver. Merino wool is naturally resistant to odor, making it a great choice for long days and providing an excellent next-to-skin feel. Flatlock seam construction minimizes chafing so you can explore in comfort whether you’re running, skiing, hiking, or just out to wander.