Collis Tool 68931 Adjustable Spindle Extension Assemblies; Shank Thread Size: 1-3/8 - 12 ; Morse Taper Size: 4MT ; Shank Length (Inch): 4-5/8 ; Flange Thickness (Inch): 3/8 ; Extension Diameter (Inch): 1-3/4 ; Extension Diameter (Decimal Inch): 1.750