Most drill chucks won't accept the 5/8"-11 thread on the Docking Drawer Counterbore Bit for Stone directly. This Shank Arbor provides the connection: a 5/8"-11 male threaded connection on one end for the bit and a 1/2" shank on the other for a compatible drill chuck. Attach the Shank Arbor, thread on the bit, and you're ready to cut.