This 3-piece HSS drill bit set is titanium nitride coated. There is an up to 6-fold increase in lifetime due to its titanium coating. These shank drills are suitable for all common drilling machines. The drill bits are high heat resistant and they can be stored in the practical storage box made of metal. Step drills: 4-12mm 3 Piece / 4-20mm / 4-32mm. Drill Set, Drill Sets, Step Drill, Step Drills, Drill Set, Drill Sets, 3 Piece Step Drill Set, 3 Piece Step Drill Sets, Titanium Drill Set, Titanium Drill Sets, Drill Bit Set, Drill Bit Sets, Titanium Drill Bit Set, Hss Step Drill Set, Hss Step Drill Sets, Step Drill Set, Step Drill Sets. .