On cold days in the mountains, you should always carry a warm, lightweight, insulating jacket that fits well under your waterproof but is small enough to stash. The Eigerjoch IN Hybrid men's jacket combines Polartec® Alpha® Direct insulating fill combined with stretch fleece inserts keep your temperature regulated, while the outer material is the water-repellent and highly abrasion-proof Pertex® Quantum Air, so you can thrutch up chimneys and swing your backpack around without worrying about your jacket surviving.View Mammut Eiger Extreme Collection Eigerjoch IN Hybrid Jacket - Men's