Got this explanation from a Google search: Filling, or batting, is a thick, often rigid material used to stuff toys, quilts, clothing and other crafts. It is made from a wide variety of materials, including cotton, rayon and polyester. Polyester filling is made from synthetic fibers, unlike cotton filling. Siliconized polyester filling is a recently developed material that helps aid in preventing allergens, bacteria and dust from attaching to the filling.
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