Arcteryx Atom LT Vest - Men's Anaconda Large ATOM LT VEST - This sleeveless core-heater hugs the body with efficient Coreloft insulation to preserve warmth while durable fleece side panels made with Polartec Power Stretch with Hardface Technology increase active use breathability and mobility. A wind and moisture resistant outer shell extends stand-alone usability. ATOM - Versatile synthetic insulated mid layers with a high degree of weather resistance. LIGHTWEIGHT - Durable, high performance with minimalist design to achieve lightweight. SYNTHETIC INSULATION - Man-made insulation with quick dry times, durability and retains warmth when damp. CUSTOMER TIPS - Our Atom LT and SL products have non-locking zippers by design. One purpose of the non-locking zipper is that it is easier to operate with one hand. This design feature also helps to limit the possibility of damage to the zipper and lightweight face fabric directly adjacent to the zipper.