When used in eiderdown comforters, eiderdown duvets and eiderdown pillows, eider down tests at approximately 700 fill power. However, because of the "hooks" in each eiderdown cluster, density and cling-power are increased, insulating at an 850 to 900 fill power. Eiderdown clutched in the palm of your hand would feel weightless, yet spread a soft, cozy heat.
As eider down is a particularly rare commodity that is one of the cushiest, lightest and warmest downs around, eiderdown comforters, eiderdown quilts and eiderdown pillows are sought after and sell at an expensive price. If you have the means, eiderdown is a sumptuous resource in which you won't regret investing.