The Best Ultralight Merino Wool Base Layer

Ibex Woolies Pro Tech Crew and matching Woolies Pro Tech Bottoms ($115) are the best lightweight merino base layer I've tested. They've been the top pick in our merino wool clothing guide for years, and I struggle to imagine what would unseat them.

Woolies are Nuyarn, which is 85 percent merino wool and 15 percent nylon. The merino wool is wrapped around a nylon core, which increases the warmth while being lighter (5 ounces for the men's large) and more durable. Woolies are 125-gsm wool (that's grams per square meter, a common measurement of fabric thread density, and therefore relative warmth). The cut here is next-to-skin tight, which is part of what I like about the Woolies—it's easy to get your next layers over them, and they don't bunch up. There are generous thumb holes on the sleeves which make it easy to ...