The Mammut Tree Wool Thermal FL Half-Zip Long-Sleeve Top builds a waffle structure into a lyocell and merino wool blend, so the fabric moves sweat away from the skin while holding onto warmth at the same time. Merino wool resists odor well enough to wear across a multi-day ski tour without reaching for a fresh layer every morning. Seamless side construction cuts down on friction points during long days of movement, and a stand-up collar adds coverage on exposed, windy stretches. What Our Gearhead(R) Experts Are Saying:"I wore this for four days straight on a hut-to-hut tour, unzipping the half-zip on every skin track and zipping back up at the top, and it never once smelled like it needed a wash. My base layer was the last thing on my mind the entire trip."