Internal Tool 64-1230-C Chamfer Mills; Cutter Head Diameter (Fractional Inch): 1/4 ; Cutter Head Diameter (Decimal Inch): 0.2500 ; End Type: Double ; Shank Diameter (Decimal Inch): 0.2500 ; Shank Diameter (Inch): 1/4 ; Shank Length (Decimal Inch): 2.