When winter temps blow in, we roll out wearing the Castelli Alpha Flight RoS Limited Edition Jacket. The performance fit and raw-edge hem keep us streamlined, while the Polartec Alpha insulation offers our chest, back, and arms moisture-managing warmth. As we pick up speed down hills, the wind-blocking power of Nano Flex Light in the chest, sleeves, and upper back stops the icy air from chilling our bones. And when we're pushing up the next climb, the double-layer construction lets air move through to keep us from overheating.