"Forcefield fabric for lightweight, breathable wind protection

Expansion vent on back for breathability"

"EXTREMELY LIGHTWEIGHT AND COMPACT
When you need protection from wind, cold or rain, the best jacket is the one you have with you. So we made this one impossibly small and lightweight. It’s windproof, water repellent and breathable, and, even better, we made it fit just right—close to body without binding. And naturally we gave it that unmistakable Castelli style."