The Cirrus Flex Vest is a synthetically insulated, warm, close-fitting vest with Thermic stretch fleece side panels for breathability. It can either be used as a super warm midlayer or an outer layer in milder conditions when you need a little more warmth but not as much as a full jacket would offer.
Cirrus is a 3M Featherless synthetic insulation that provides a high performance alternative to natural down. It was designed to mimic the look and feel of natural down with all the benefits and none of the drawbacks. It retains two times the loft of down when wet, breathes superbly, has no allergens, retains warmth even when wet (more so than Hydrophobic down), compresses easily and dries exceptionally quickly. If you were to compare Cirrus to down insulation, a fill power of at least 600 would have to be achieved to match the warmth of Cirrus.