Titanium nitride coating runs cooler and lasts longer Automatically deburrs holes Spiral Flute design is better for faster drilling Replaces 29 individual drill bits 4241 High Speed Steel size: Drill 1 x 4mm to 32mm, 15 Steps, Increments of 2 , 10mm Shank Drill 2 x 4mm to 20mm , 9 steps , Increments of 2 , 8 mm Shank Drill 3 x 4mm to 12mm, 5 Steps , Increments of 1, 6 mm Shan HSS Metric Spiral Flute Step Drill Bit Set 4241 Steel Titanium Coated Step Drill Bit Set