A down vest is a staple whether you're climbing, hiking, ski touring, or alpine climbing. And while most vests are fairly basic in design, the Arc'teryx Men's Thorium SV Vest improves on the tried and true through a careful design that yields an exceptional warmth to weight ratio and highly water resistant construction. Arc'teryx used a combination of down throughout the body and Coreloft synthetic fill in areas prone to moisture. To prevent heat loss, the Thorium features a box walled baffle construction to eliminate cold spots that result from a traditional stitch through baffling. An athletic fit keeps the jacket close to optimize insulation and allows it to be worn comfortably as mid layer on an exceptionally cold day. When not in use, the vest packs inside of the included stuff sack, which can be stored in the zippered chest pocket, so you can throw it in your pack, without it taking up too much space.