This sleeveless jacket incorporates Polartec Alpha technology to provide warmth and thermoregulation, preventing overheating during intense efforts such as climbs. The Polartec Alpha membrane blocks wind while remaining breathable. Lightweight back construction optimizes protection without the risk of overheating. Ideal in combination with our long-sleeved jersey, this jacket provides optimum protection for winter outings. Originally designed for US special forces, the Polartec Alpha membrane is insulating, water-repellent and efficiently wicks away perspiration to maintain body temperature.