When there's a bite in the air and fast descents are on the menu, we zip into the Castelli Alpha Flight RoS Jacket. The thermal lining helps hold in warm air, while the double-layer construction invites fresh air to cycle through, ensuring we don't overheat on the climb. As the road slopes down, the material's tighter weave helps dull the icy wind of speed. Constructed with ultralight materials and a raw hem, this jacket feels like a whisper as it regulates our body temp through our intense winter training sessions.