"The Diamond Peak Pro Long-Sleeve Crew, part of Columbia's Titanium line, builds around Omni-Freeze Zero Ice, a touch- and sweat-activated cooling technology. The technology engages as effort and temperature shift on the trail, activating on contact with moisture to deliver industry-leading cooling through fast pace changes and unpredictable conditions. What Our Gearhead® Experts Are Saying:""I stopped worrying about sunburn on my arms once I started wearing this, since the UPF 50 rating covers what my sleeves reach. The Skin Cancer Foundation actually recommends the fabric, but I still put sunscreen on my hands and face because the protection stops where the shirt does."""