Irwin Tools 10502ZR Unibit Sheet Metal Step Drill Bit Set is a selection of the most popular Unibit step drill bits in the low diameter range (below 7/8"). Ideal for drilling true round holes with precise control in a variety of materials like sheet metal, metal plates, aluminum, fiberglass, plastics, plexiglass and wood. The specially designed cutting edge drills true, round holes for a smooth, clean finish and the SpeedPoint tip penetrates fast, prevents "walking," and eliminates the need for a pilot/starting hole. The hex shank provdes a secure grip in the drill chuck. Plus, the permanent laser-etched sizes inside the flute are easy to read for precise control during the hole enlarging process.