Duplex Board is a kind of paperboard or cardboard, also named greyboard, due to its double side grey color. It consists of two layers, or plies, so people call it duplex board. The exterior one side of the board often is coated with a bright white appearance to give it a glossy sheen.Duplex board is tough, thin and able to take on a bright white appearance, unlike common corrugated cardboard. It is commonly used to create boxes for a variety of small goods. For example, it is often used in pharmaceutical packaging.