The filling power-measures in CUIN, is the primary scientific standard for the quality of down. The higher the filling power, the better the quality. At the same weight, Moscovy Duck Down is several times more voluminous with a much greater filling power (>800 CUIN), making it fluffier. Thus, the duvet is perceptibly lighter with the same thermal performance.

The best duvet is the one which has the highest thermal insulation property at the lowest weight.