Irwin Step Drill Bits are designed for precise drilling in thin materials and have a single flute for maximum drilling control into sheet metal.
The drill bits have a unique flute design which ensures that they drill perfect round holes into sheet metal.
A fluted shank also prevents the drill bit from slipping in the chuck. They also have a self-centring point which ensures that they will not walk and which eliminates centre punching.
The drill bits are made from industrial grade M7 high-speed steel, and are available in different step increments(between 1-3mm).

The IRW10502855 Step Drill Bit has the following specifications:
Number of hole sizes: 10.
Hole diameters: 5, 7.5, 10, 12.5, 15.2, 18.6, 20.4, 22.5, 25.5 and 28.3mm.