Micro 100 QD2-MR16-8-1000 Boring & Grooving Bar Holders; Inside Diameter (mm): 12.7000 ; Inside Diameter (Inch): 1/2 ; Inside Diameter (Decimal Inch): 0.5000 ; Outside Diameter (Decimal Inch - 4 Decimals): 1.0000 ; Outside Diameter (Inch): 1 ; Overal