warmest mountaineering mid layer jacket. This is Norrona most flexible and warmest fleece jacket designed for mountaineering, with the highest warmth-to-weight ratio in our collection. The jacket features a stylish retro design, also making it perfect as a warm everyday garment for city life and travel. We use the Warm3 fabric because it is lightweight and highly insulating. Its durability and excellent flexibility ensure the jacket to maintain a great look, even after extended use. Key features include two hand-warming pockets, a chest pocket, integrated hand gaiters and a warm, protective collar. This jacket has a regular fit.