Serious mountain travel requires an insulated piece with exceptional warmth-to-weight value. The Fission SL is our lightest, fully waterproof, insulated jacket that is outstanding in cold wet weather. GORE-TEX full storm weather protection is teamed up with our exclusive laminated ThermaTek non-quilted insulation. The result is evenly distributed warmth that can stand up to anything. No cold spots. There are times when you're working hard but you can't or don't want to remove your insulation. Pit zips let you vent heat rapidly, extending usability on cold days. The insulated StormHood takes care of wind and storms with a fully secure, helmet compatible shelter. Often this is the at base camp or sitting out a storm piece, so we've included two zippered hand pockets, two internal mesh dump pockets, WaterTight Vislon centre front zipper, and an invaluable hem drawcord that allows you to really bunker down and have what you need at the ready. The Arc'teryx helmet compatible Stormhood is designed to provide the ultimate protection in cold or wet weather. The laminated brim and hood adjusters secure tightly and deliver full coverage without restricting movement or visibility. Exclusive to Arc'teryx, Thermatek is a continuous filament, synthetic insulation that is treated with DWR (Durable Water Repellent) to make it hydrophobic, which means that it repels moisture very efficiently. The lofty insulation is then laminated to a backing fabric to ensure an even distribution and insulation. Standing in as our "Arc'teryx Standard" fit, the complex patterns used utilize anatomical shaping and gussets to enhance motion and eliminate excess bulk. Trimmer than the Relaxed fit with room for a base layer, a light fleece mid-layer and a synthetic or down filled mid-layer. Materials: N40p-X GORE-TEX 2L. ThermaTek 2.7 oz-100% nylon face, 92 g/m2.