The old adage 'cotton kills' isn't just an alliterative joke. Your choice of top will determine more about your day than you care to think. The Arc'teryx Men's Morphic Zip Neck Top kills cotton. Unlike cotton, the brilliantly engineered and lightweight Enduraflex and Phasic AR X fabrics wick moisture, dry quick, and allow air flow, minimizing odor retention and virtually eliminating water absorption. Stretchy, hard wearing Enduraflex material in the abrasion prone areas in the forearms ensures that brushes with rock faces won't shred what is sure to become your go to climbing shirt. And UPF 50 rated sun protection means you can stay out on the crag all day without worrying about sunburn.