An article for mixing a tray holder has a generally rectangular side panel having upper and lower edges and inner and outer faces, a generally rectangular roof panel projecting generally perpendicular from the inner face of the side panel along the upper edge thereof, and a generally rectangular floor panel projecting generally perpendicular from the inner face of the side panel along the lower edge thereof. These panels are formed along a plane perpendicularly to and bisecting all panels with a weakened region and the roof and floor panels have straight outer edges remote from the side panel that are complementarily shaped to opposite sides of the plane. Thus according to the invention the article can be subdivided into two complementary and interfitting pieces along the plane adn joined together to make a half-depth holder by bonding together the complementary outer edges. A full-depth holder can be made by bonding together the outer edges of two such articles. Thus it is possible with a single such article made by a single mold to make single or double-depth holders. Manufacturing costs are thereby held down.