Step drills are the only drills you can sharpen yourself (both tip and flute). Exlusive single radial concave flute crates perfectly round holes in metal, plastic wood and other thin materials without center punching. Contructed of industrial grade high-speed molybdenum steel, heat-treated and temperature for long life. Slef-stating tip. No center punching needed. Automatically deburrs top side of hole. Ideal for steel, copper, aluminum and other thin meterials. Single flute cutting edge with sizes printed on each step 3 flatted shank Size #4, 3/16 to 7/8 by 1/16 Increments Drill up to 12 different size holes 3/8" Shank