The Icebreaker Merino 260 Vertex Alpine Geo Half Zip adds a zip to a warm, 100% Merino base layer, so a hard climb on skis or snowshoes doesn't mean overheating before the descent even starts. Gusseted underarms, flatlock seams, and offset shoulder seams keep the fit moving cleanly through the deep, repetitive motion of a real day on snow, not just standing around in the cold. Merino's natural odor resistance means the same top holds up across a full trip, not just a single outing. What Our Gearhead(R) Experts Are Saying:"I unzipped halfway up a skin track when I started sweating and zipped back up the second I stopped moving at the top. That kind of control is the whole reason I reach for a half-zip over a crew on a big climbing day."