Micro 100 THSL-5-787 Boring & Grooving Bar Holders; Inside Diameter (Decimal Inch): 0.3125 ; Outside Diameter (mm): 20.0000 ; Overall Length (Decimal Inch): 5.7500 ; Overall Length (Inch): 5-3/4 ; Head Diameter (mm): 20.0000 ; Shank Length (mm): 146.