Whether we're gearing up for a cold day at the resort or heading out on a brisk fall hike, the Smartwool Classic All-Season Merino 1/4-Zip Base Layer is prepared to keep us warm through it all. Built with a blend of merino wool and nylon, we are provided with unmatched warmth, odor control, and long-lasting durability, while its flatlock seam construction and offset shoulder seams minimize chafing for all-day comfort.