From a harsh winter trip to get a glimpse of the Northern Lights to spring morning trail runs, The North Face Mens Borealis Zip Top has your core covered, literally. Breathable polyester fleece provides the warmth, while stretchy elastane panels under the arms and at the lower back stretch and move with you when you hit your stride. UPF 30 throughout blocks the sun and bamboo carbon within the moisture-wicking panels fights funk. As an underlayer or active top, nothing beats the thumb holes; they keep the sleeves in place.