Containerboard, also referred to as CCM or corrugated case material, is a type of paperboard specially manufactured for the production of corrugated board. The term encompasses both linerboard and corrugating medium (or fluting), the two types of paper that make up corrugated board. Since containerboard is made mainly out of natural unbleached wood fibers, it is generally brown, although its shade may vary depending on the type of wood, pulping process, recycling rate and impurities content.