Ginsco 3Pcs 1/4 Inch Hex Shank Step Drill Bit Set 4-12/4-20/4-32mm HSS Titanium Coated Surface Treatment: Titanium Coated Shank Size: 1/4" Hex Shank Two flute design provides faster, smoother and cleaner cuts each step is clearly labeled with the depth diameter in steps. It is very suitable for using to cut holes in a variety of materials including steel, brass, wood, plastic, etc. They also help to enlarge existing holes