General description The Irwin Step Drill Bit is designed for precision drilling with a range of hole sizes, making it ideal for various DIY and home improvement projects. Technical specifications Number of hole sizes: 10 Hole diameters: 5 mm, 7.5 mm, 10 mm, 12.5 mm, 15.2 mm, 18.6 mm, 20.4 mm, 22.5 mm, 25.5 mm, and 28.3 mm