Leading you to an educated decision.

Hex Shank
The flats of a hex shank can either be machined on a round shank, or can be the natural flats of hex bar stock. A hex shank can be grasped by a 3-jaw drill chuck, or can be held in a custom chuck specifically for hex shanks. 1/4 inch hex shanks are common for machine screwdriver bits, and have spread from that application to be used for drill bits that are compatible with screwdriver machinery.