The substrate size for photomasks is determined by the exposure machine and the exposure method. For small photomasks (7 x 7 inches or less) the sizes have been standardized, with 4-inch, 5-inch, 6-inch, and 7-inch sizes, and thicknesses of 1.5 mm, 2.3 mm, and 3.0 mm generally being used. Depending on the exposure equipment, masks with sizes and thicknesses larger than that are also quite numerous, and can be cut into specific sizes after imaging. The tables shown below are the general standards.