Ever wonder why a down blanket or comforter is so warm on a cold winter night? It’s because they’re made from one of nature’s best insulating materials. - Down is classified by weight and fill power. Fill power is a measurement of efficiency: the higher the fill power, the better the down and the greater the insulating value. Fill power represents the number of cubic inches filled by an ounce of down, and it is directly related to the size of the down cluster. The higher the fill power, the larger the clusters, and the more air that is trapped between the clusters. The trapped air is what gives down its insulating properties. - The size of the bird and the climate in which it lives determines the size of its down cluster. The colder the climate, the larger the down cluster required to keep the bird warm. To protect your down comforter, we recommend a duvet cover. To protect and extend the life of your pillows, pillow protectors are an essential.