MemBrain® Waterproof/Breathable Fabric
Marmot 700 Fill Power Down
Fill power is perhaps the most commonly misunderstood purchase decision factor. Usually a manufacturer will advertise a "fill-power" of 650, 700, 850 etc. These numbers are a reference to the quality of the down insulation used. The number is actually a volume — the amount of cubic inches one ounce of down occupies. For example, one ounce of 800 fill-power down will occupy 800 cubic inches when compressed by a standardized weight. If you use two ounces of 800 fill on jacket A, and two ounces of 700 fill on jacket B, jacket A — with the 800 fill down — will be warmer because it has more loft. However, a jacket may have eight ounces of 850 fill down and yet be of similar warmth to a jacket with twelve ounces of 650 fill down. The jacket featuring 850 fill down has similar warmth but will weigh less, and be more compressible, since it has less down in it. In other words, higher fill power down allows for better warmth-to-weight ratios, but is not always the definitive factor when considering warmth of a jacket.