Tool-Flo 1271379 Helical Flute Thread Mills; Material: Carbide ; Thread Size (Inch): 5/16-18 ; Thread Type: Internal ; Shank Diameter (Decimal Inch): 0.2500 ; Cutting Diameter (Decimal Inch): 0.2360 ; Length Of Cut (Decimal Inch - 4 Decimals): 0.6700