When a down comforter is made, the top and bottom are sewn together most of the way around. A small approximately 6" hole is left open. The feathers are then blown into the opening and the opening sewn shut. Some are made with multiple baffles, which are filled and sewn shut separately. In Germany, as I'm sure in other European countries, you can order your down comforter with the exact covering, feather and weight you want, lighter weight for summer or heavier for winter.