What Our Gearhead(R) Experts Are Saying: "Warmth-to-weight is stellar. It compresses to a true 'small' and still handles frosty starts."We chase shoulder-season summits with the Spark 15F Down. High-loft fill, efficient baffles, and a streamlined cut deliver serious warmth without taxing pack space. Draft controls fine-tune comfort when temps hover well below freezing-ideal for fast, cold itineraries.