Designed for rotary or percussion drilling. Negative back grinding enables tip to bore through materials with a filing action. Cobalt and tungsten carbide drill bit tip designed for maximum hardness, wear and resistance to heat up to 2000 F (Degree Fahrenheit) Resharpenable. Chrome vanadium steel shank for strength and flexibility. Bit has a flat bottom parabolic flute for faster waste removal. Drills through hardened steel, ceramic tile, marble, plastic, cast metal, concrete, glass, plexiglass, granite, fiberglass, brick, masonry, PVC (polyvinyl chloride), and wood. Conforms to ANSI (American National Standards Institute) standards. Set includes 1 each: 1/8", 3/16", 1/4", 5/16", 3/8".