With light and compact warmth as the goal, Arc’teryx combined the lightweight performance of Coreloft™ synthetic insulation, an ultralight Arato™ nylon shell and highly efficient ergonomic patterning to create an alpinist’s hooded belay jacket that packs to the size of a water bottle and delivers effective warmth for just 220 grams. Articulated patterning and gusseted underarms provide extended mobility without sacrificing coverage. The fit is women’s specific to optimize performance and comfort, and the Arc’teryx Trim fit with e3D fit accommodates layers, but stays close to the body for a higher level of thermal efficiency with minimal bulk. Arc’teryx e3D (ergonomic 3-Dimensional) patterning utilizes extra space in key joint areas to bring an added level of use specific articulation. OPTIMIZING INSULATIONPurpose driven design means using materials that perform, and employing them in the best ways possible. In the Nuclei FL’s case, utilizing different volumes of Coreloft™ insulation helped Arc’teryx reduce weight and bulk without sacrificing effective warmth. Mapping the insulation to place specific weights where they deliver the most appropriate benefit, they placed loftier 80g Coreloft™ in the body where a higher level of warmth is needed and bulk is less of an issue. Lighter, more compact 60g Coreloft™ insulates the sleeves and side panels to aid air permeability, streamline fit and improve mobility.STREAMLINED FEATURESDisciplined in its design, the Nuclei FL is as streamlined as possible. Simple elastic binding around the cuffs and hood is light, smooth and creates a secure fit. Hand pockets have streamlined, invisible zippers that stay out of the way of rope and rock. The Nuclei’s internal pocket includes a removable stuff sack with a carabiner clip loop that allows it to be easily fastened to a harness or pack. The Arc’teryx No Slip Zip™ secures the closure with a series of small bumps spaced every twelfth tooth to secure the slider and prevent self opening but still unzips with a single hand for rapid ventilation.