Milwaukee 19 Piece Drill Set
(with metal storage case)
HSS - Cobalt
Cobalt drills are a preferred drill for harder materials especially stainless steel. The primary reason for this being they hold there rigidity and hardness at a higher temperature than HSS drill bits. Cobalt drills are more suited to CNC machines, Pillar Drills and Drill Presses due to the brittleness of the material compared to standard HSS.
Under equivalent usage cobalt drills will out preform & outlast Standard drills by some margin.