Micro 100 TD1-MR16-4-750 Boring & Grooving Bar Holders; Inside Diameter (Inch): 1/4 ; Inside Diameter (Decimal Inch): 0.2500 ; Outside Diameter (Decimal Inch - 4 Decimals): 0.7500 ; Outside Diameter (Inch): 3/4 ; Overall Length (Decimal Inch): 3.2000