The Arc'teryx Atom Jacket provide super packable, lightweight construction with insulated warmth. Those are two of my favorite things. The secret of making these jackets so amazingly awesome lies in the Polartec Power Stretch Fabric with Hardface Technology. Shhh... don't tell anyone I told you. Here's a breakdown the the Atom jackets.
Arc'teryx Atom LT Jacket - Light as light can be, the Arc'teryx Atom LT is available as a regular jacket or a hoody. The hoody has a scuba style hood, that fits nicely under a helmet. Anyway, it's Polartec Power Stretch for wind and moisture blocking goodness, coupled with 60 gm Coreloft insulation for warmth. Wear the Atom LT Jacket alone, or as insulation under an Arc'teryx Hard Shell for severe mountain conditions.
Arc'teryx Atom MX Jacket - The Atom MX Jacket has warm synthetic insulation in the arms and upper torso with durable Polartec Power Stretch fleece on the side panels and forearms. That pretty much spells versatility and mobility. The Polartec is abrasion resistant, so the Atom MX can stand up to serious conditions and a backpack. The bottom 1/4 of the jacket is lightly insulated with brushed tricot for sleek layering under a harness or hipbelt. How cool.
Arc'teryx Atom SV Jacket - The Atom SV is signficantly warmer and more protective than a fleece, so you can wear it as a killer midlayer in fridgid conditions, or as a stand-alone jacket when it's milder. The Atom SV is packed with 100 gm synthetic Coreloft insulation that packs small and keeps you warm. A light tricot underarm panel enhances breathability.