The Smartwool Active 1/4-Zip Top blends merino wool with TENCEL(TM) lyocell to move moisture, regulate temperature, and resist odor through hard efforts and easy days alike. Targeted mesh zones open up breathability exactly where the body runs hottest, so the fabric works with the effort instead of trapping heat against it. Offset shoulder and side seams keep the fit smooth and chafe-free over long miles, and a regular fit leaves room to move without adding bulk. What Our Gearhead(R) Experts Are Saying:"I wore this on back-to-back training days without a wash, and it still smelled clean after the second run."