Gear Review: SmartWool NTS Microweight Crew

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When it comes to warmth-to-weight ratio, nothing beats a superthin merino layer. And among the wool tops we tested, this sheer 18.9-micron shirt was the clear favorite. “I never took it off during a four-day climb of Rainier,” says a tester. “I wore it while climbing, snuggling in my bag at night, and resting at Camp Schurman in the intense sun. And I never felt clammy, even when I was huffing hard during the summit push.” Stink build-up was a nonissue, as is typical for wool, and the almost-sheer fabric is deceptively durable; it showed no snagging or pilling. Upgrade to the zip-T version ($75) for more ventilation and versatility. $65; 5.2 oz.; m’s S-XXL, w’s XS-XL; smartwool.com