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Down quality is rated by a system that measures its fill power, which is the number of cubic inches displaced by an ounce of down. It is usually expressed with the word "fill" preceded by a number ranging from 300 to 900, increasing in increments of 50. The higher the fill-power, i.e. 800 fill, the greater the loft provided by the down, and therefore the less down it requires to provide warmth. Typically 550+ fill is sufficiently warm and light enough to be used in jackets intended for activities like backpacking and climbing. At the higher end of the scale, 800 to 900 fill down is often used for extremely lightweight and warm clothing. In this jaket is 800 fill Power.