Packing generally refers to the material that is filled in other objects. In chemical engineering, packing refers to the inert solid materials, such as Bauer ring and lacI ring, which are packed in the packed tower. Its function is to increase the air-liquid contact surface and make them strongly mixed with each other. In chemical products, (filler), also known as packing, refers to the solid materials used to improve processing performance, mechanical properties of products and (or) reduce cost. Among them, packings that can significantly improve the strength of products, such as long fibers and whiskers, are often called reinforcing materials, and carbon is called reinforcing packings. Solid materials and calcium carbonate are often added to pharmaceutical tablets, cosmetics and detergents as packings, but the purpose is to adjust the concentration of the agent rather than improve the performance, so it should be called diluent. Although plastic plasticizers, rubber oiling and spinning finishes can improve performance and affect costs, they are traditionally regarded as processing aids.

In polymer chemical industry, packings (packings) are the most used additives. Almost all plastics (including thermoplastic), natural rubber and coatings use a lot of packings.