The design and shape of the materials in which a product is packaged. Product configuration, the design and shape of the product itself, may also be considered a form of trade dress.
The Lanham Act protects trade dress if it serves the same source-identifying function as a trademark. It is possible to register trade dress as a trademark, but for practical reasons most trade dress and product configurations are protected without registration under 15 U.S.C. § 1125(a).