Wire gauge twist drills cannot be held in collet-type handpieces without an Adaptor Chuck. Available in 2 sizes, the smaller of which (item 200-740) is preferred for the smallest drills (wire gauge sizes 60 through 80) to minimize run-out. The larger Adaptor Chuck (item 200-741) is furnished with 2 collets. Both models have 3/32" (2.35 mm) shanks.