This technical, cold-weather base layer top is for highly aerobic days, the 260 Zone Long Sleeve Half Zip features zoned ventilation panels for active temperature regulation and ample breathability. Icebreaker BodyFitZone™ - features breathable zones for high intensity activity Thumb loops keep your sleeves in place and hands warm Raglan sleeve construction for mobility Gusseted underarms for mobility and comfort Flatlock seams to prevent friction Zipper chin guard to prevent friction Drop tail hem for added coverage