Used for Flexographic printing. Usually one block is required per colour each side of the bag being printed. Also called stereos, printing plates or "Cyrels", which is the name given by Dupont to their stereo material product. Broadly, blocks cost according to their size, which is dictated by the size of the image to be printed. The blocks are placed on a cylinder which rotates, collecting ink from the Anolox, and place the ink on the substrate.