Internal Tool 64-2770 Chamfer Mills; Cutter Head Diameter (Fractional Inch): 5/16 ; Cutter Head Diameter (Decimal Inch): 0.3125 ; End Type: Single ; Shank Diameter (Decimal Inch): 0.3125 ; Shank Diameter (Inch): 5/16 ; Shank Length (Decimal Inch): 2.