Grey Down One Layer Duvet - SDA lightweight comforter using down from free range grey ducks. Grey duck feathers, which grow healthily in nature and are close to the original species, are said to be stronger and less likely to settle. This lightweight, thin down comforter can be used year round in combination with blankets. They are also compact and can be stored without adding bulk. MUJI sizes are different than North American sizes. Please check the measurements before