Updated to give it greater versatility the Smartwool Merino 250 Baselayer Men's 1/4 Zip is one of Smartwool’s heaviest baselayer tops and best among the best base layers for cold weather. Made from 100% merino wool for cozy comfort and wicking breathability in a natural fiber piece this shirt has flatlock seam construction to minimize chaffing and a high zip neck for temperature regulation. This is a slim fit.. if you want to get the most versatility out of this piece, since it has the feel of a featherweight sweater, and you are in-between sizes, size up. This will give you space for adding a featherweight layer underneath for those days when a heavier midweight is too much, but a baselayer isn’t enough, and turn this into a light sweater you can pull on this summer over a tee. For relentless flexibility in a packable, functional, piece, which also looks very nice on, this piece fills the place of a light summer sweater, a heavy winter baselayer, and a light winter midlayer. It’s no wonder this remains one of Smartwool’s most popular pieces.