Drillpro Titanium Step Drill Bit Cone Drill Bits, High Speed Steel 10 Steps 1/4&rdquo; to 1-3/8&rdquo; INCLUDES 10 STEP SIZES: 1/4", 3/8", 1/2", 5/8", 3/4", 7/8", 1", 1-1/8", 1-1/4", 1-3/8" TRI-FLATTED SHANK: fits into power tools chuck securely and eliminates slip. TITANIUM | HIGH SPEED STEEL: classic high speed steel with titanium coating for proven capability and durability in drilling holes in plastic, aluminum, copper, stainless steel and many other types of sheet metal EASY DRILLING: Two-fluted design provides faster, smoother cutting;Provided with small pressure and the sets can cut through wood, sheet metal, steel and other surfaces. Mainly used for drilling within 3mm of thin steel drilling, a drill can replace the use of more than a bit, according to the need to process different diameter holes, and one-time processing can be completed, do not need to replace the drill bit and positioning holes