Arcteryx says about the Atom LT Hoody Men's
The Proton LT Hoody is equipped with a breathable insulation package to manage the dynamic needs of mountain pursuits and perform as a self-regulating mid layer for a variety of high output activities. Breathable insulation means excess heat and moisture can pass through the combination of air permeable fabrics and insulation. In addition to being extremely air permeable, the Fortius™ Air 20 face fabric has unrivaled hardwearing durability, over 60 times more durable in abrasion tests than the industry standard. Coreloft™ Compact 80 synthetic insulation in the body maintains excellent stretch recovery. The No Slip Zip™ keeps the main zipper from self-opening and the helmet compatible insulated hood gives additional warmth. Put it on, leave it on and stay focused on the activity.