Base layer or only layer, this cold weather essential performs as it warms. Made partially from wool, midweight knit naturally resists odor, dries quickly, and regulates temps so you can keep moving. Nifty thumbholes protect your hands. At day&';s end, hang up the top by a loop in the back. We love it for: cold weather running 86% recycled polyester & 14% wool Warm, quick-drying, odor-resistant & temperature-regulating Tailored fit Comfort neck tape reads "born to run free" V-notch at back collar & side seams Locker loop Elbow patches Thumbholes in cuffs Rounded back hem Machine wash cold, air dry, don&';t bleach, mmkay? Designed in California, made abroad For a looser fit, size up.