The Ayacucho 10Y Mount Everest Jacket is an insulation jacket that contains no down but packs down to a small size. You can wear it as an outer jacket on dry days, while it makes a great mid layer when the weather is cold and wet. This jacket probably isn't warm enough to get you to the top of the world's highest mountain, but you can certainly take it with you on your way to base camp, and for your other outdoor activities. The DuPont Sorona® insulation is produced with tomorrow's world in mind. Sorona® is bluesign® and Oeko-Tex® certified, and made of 37% renewable, plant-based materials.Less energy is required to produce this fibre, and the CO2 emission is about 60% lower than in the production of other comparable fibres. This technical filling is light, warm, breathable and quick drying.