Micro 100 TD1-MR8-5-625 Boring & Grooving Bar Holders; Inside Diameter (Inch): 5/16 ; Inside Diameter (Decimal Inch): 0.3125 ; Outside Diameter (Decimal Inch - 4 Decimals): 0.6250 ; Outside Diameter (Inch): 5/8 ; Overall Length (Decimal Inch): 3.2000