The Men's Atom LT Hoody from Arc'teryx is a trim hybrid hoody which is designed as an active-use insulation layer, providing vital core warmth with liberal mobility and breathability. Lightweight and compressible, the Atom LT Hoody features Coreloft insulation in the torso, arms and hood. The side panels and underarms feature Polartec Power Stretch with Hardface Technology, delivering stretch mobility and breathability to help regulate temperature during exertion. A wind and moisture resistant taffeta outer shell extends stand-alone usability. Read more… The benefit of taffeta fabrics is their light, airy nature with an ability to turn aside wind. Highly compressible, it packs down into a tiny parcel of stored warmth. A quick shake restores the original loft, time and again.