Disc shaped magnets are a convenient and popular shape. The size of a disc is given by specifying the Diameter x Thickness. Most discs are magnetized through the thickness, so that there is a North pole on one flat surface, and a South pole on the other. If a disc is magnetized through the diameter (north on one edge and south on the opposite edge), then it will be clearly marked. Discs magnets are the most economical magnet for the most common holding applications.