The warmest option in the Atom series performs as a standalone or midlayer. Atom Series: Synthetic insulated midlayers. Always warm, breathable and wind resistant, worn as a midlayer or standalone - the Atom Heavyweight Hoody is one of our most versatile insulation pieces. Its Coreloft synthetic insulation is efficient, effective and resilient. Mapped for optimal performance, it works well even if wet. The lightweight, wind resistant and water repellant Tyono 30 shell is treated for extra durability, and Permeair panels under the arms add ventilation. The insulated, helmet compatible hood adds warmth and protection.