Micro 100 QD1-MR16-4-787 Boring & Grooving Bar Holders; Inside Diameter (Decimal Inch): 0.2500 ; Outside Diameter (mm): 20.0000 ; Overall Length (Decimal Inch): 3.2000 ; Head Diameter (mm): 0.2500 ; End Type: Double ; Sizes Included: 0.2500 Side A; E