Bordo Drill Set - Reduced Shank 16-25mm 4 pce ½inch– Metric 2654-S1118 notched point 30 helix reduced shank drill. BRIGHT BLACK FINISH These drills are ground and then a black finish is achieved by steam tempering, a thermal process resulting in a porous tool coating. This surface aids chip flow and heat dissipation. The drill is then ground a second time to achieve a bright finish on the shank and cutting edges. Includes: 16mm, 18mm, 22mm, 25mm Flute length: 89mm Overall length: 152mm