Our lightest insulated jacket excels in all mid-output mountain activities. From shoulder-season hikes to easy winter runs, its recycled stretch insulation delivers targeted warmth to your core without limiting mobility. Uninsulated sleeves and stretchy, fleece-lined side panels boost breathability and make for easy overhead movements. Made for hikers. Loved by athletes, runners, skiers, and guides. Need a heavier option? Try the Atom Jacket .