Incredibly light and packable, the 850-fill Arc'teryx Women's Cerium LT Vest weighs just 105 grams but provides exceptional warmth for its weight. Designed as a minimalist mid layer for cold, dry weather, its packability also makes it useful as a lightweight warming layer for autumn belays, evenings at camp and backcountry ski rest periods.The unique, exceptionally light Arato 7 nylon shell fabric is a highly compressible fine denier taffeta that provides remarkable durability and windproof properties. Because the Cerium LT Vest is intended as a mid layer, Arc'teryx is able to use sewn through construction to further reduce weight and increase packability. True to detail, the vest's zips are minimised to reduce weight and bulk.Down Composite Mapping technology is used to strategically place synthetic Coreloft insulation in areas prone to moisture. The internal pocket zips closed and includes a removable stuff sack. A simple elastic binding at the hem seals out drafts without the bulk of cordlocks, and the collar is carefully patterned to provide coverage while layering comfortably under a shell. A DWR treatment adds moisture protection.