Micro 100 QT-187-C3 Boring & Grooving Bar Holders; Inside Diameter (Inch): 3/16 ; Inside Diameter (Decimal Inch): 0.1875 ; Outside Diameter (Decimal Inch - 4 Decimals): 1.2598 ; Overall Length (Decimal Inch): 2.4729 ; Head Diameter (Decimal Inch): 0.