According to ADA Specification No. 28, what is the rate of increase in file diameter per running millimeter of length for a K-type file from point D0 to point D16?
Each number should represent diameter of instrument in 100th of millimeter at the tip. 
For example, a No. 25 K file shall have 0.25 mm at D1 and 0.57 mm (0.25 + 0.32) at D2. 
These sizes ensure a constant increase in taper, i.e. 0.02 mm/mm of the instrument regardless of the size.