The Spark helps you sleep well, even when the mercury falls to 15 degrees. With Partial Flex construction you'll sleep more comfortably and more warmly than ever before. All without adding noticeable weight! We generously fill the continuous baffle construction with 800-fill down, distributing more through the torso to bolster warmth. The down-filled draft tube and Jacket Hood take a miserly approach to your body's warmth—they horde it greedily! Twenty-denier shell material won't sprout down, resists tears, and saves on weight, too. The Spark stuffs to a tiny seven-by-17-inch package.