When doing technical climbing in severe cold conditions, you need to keep warm, but you don't need weight. The Summit Breithorn down jacket is made of 800-degree ProDown? insulation for warmth and weight. It provides a high level of warmth and compressibility while maintaining bulkiness, even in humid conditions. Comes with raglan sleeves that allow you to fully lift your arms. We have also added underarm lining to allow you to move freely while climbing. If it's too hot and sweaty, you can put this lightweight jacket in your pocket just in case. Not only that-recycled materials make it more natural.