Our most technical high-alpine insulation jacket, built for year-round mountain use as either a standalone piece or an insulating layer under a Gore-Tex shell on the coldest days. Made from Pertex 20D Quantum with Diamond Fuse technology, the tightly woven outer fabric strikes a refined balance between protection and breathability, while the uniquely engineered yarn structure increases durability without adding unnecessary weight. Finished with a classic diamond quilt and 800 fill power RDS-certified down, it delivers serious warmth in a clean, lightweight package.