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.