*Spandex This stretchy polyurethane fiber (aka elastane or Lycra) provides stretch to fabrics. Downsides: It absorbs odors and dries slowly.
On multiday backpacking trips, many hikers—our testers included—favor wool baselayers because the natural fiber can be worn for days on end with relatively little stink. The Koli, which is made with superfine (18.9-micron), exceptionally soft merino, impressed our sweaty canyon hikers with above-average odor resistance, as well as superb wicking and comfort.
“I wore it for 18 days straight doing high-intensity Nordic skiing, and remarkably, it did not smell,” reports one tester who took the shirt off and allowed it to air out at night but didn’t wash it. Why the exceptional anti-stink performance? The Koli is 100 percent merino, whereas most other wool tees have some spandex* for stretch. Testers noticed the difference. Downsides? It’s expensive, and after five months of intense use, our samples began to pill on the shoulders, where pack straps rub. Fit is snug. $100; 5 oz. (m’s M); m’s S-XXL, w’s XS-XL; golite.com