The Helly Hansen Lifaloft Hybrid Insulator jacket pairs Lifaloft synthetic insulation with stretch, slick-face fleece panels, so the panels that need to move stay flexible while the panels that need to trap heat stay warm. At roughly 15 ounces, it packs down small enough to stash in a pack for later, and a PFC-free DWR treatment sheds light moisture without adding weight or bulk. The hybrid build works as a standalone layer in milder cold and slides easily under a shell once temperatures drop further. What Our Gearhead(R) Experts Are Saying:"I wore this on its own through a mellow spring lap and didn't think twice about the cold, then zipped a shell over it two weeks later on a colder day and never felt like the extra layer was fighting my shoulders. The fleece panels flex right along with me instead of bunching up under a pack strap."