real Down Insulation "Aspen and Windham" For centuries, humans have used down feathers for insulation. Down's breathable, lightweight, resilient and form-fitting properties make it one of the best insulation materials available and if properly maintained it can retain its loft for up to three times longer than most synthetic fiber insulation. The Aspen jacket and the Windham vest has 600 fill power insulation. Fill power measures the loft or “fluffiness” of a down product. The higher the fill power, the more insulating air pockets the down has. At 600 cubic inches per ounce, the insulating power of Aspen and Windham is considered among the best.
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