Awesome lightweight Merino wool base layer from Smartwool. Great next-to-skin comfort in warm or cold conditions. Smartwool was the first company to use Merino wool in socks, and is now the undisputed number one brand of merino wool baselayers.  With the extreme comfort of merino wool over and above the itchy and scratchy wool of days of old, the majority of our customers now prefer merino wool to meet their primary base layer needs.