This 4-Piece glass and tile drill bit set from Mibro - a 60 plus year old company selected as one of Canada's "50 Best Managed Companies" contains 1/8-Inch, 3/16-Inch, 1/4-Inch, and 5/16-Inch drill bits. They have a carbide spear point with a uniquely sharpened edges for easy penetration in glass, mirrors, ceramic tiles and other hard brittle materials like Stucco. They cut a perfectly round hole with out chipping or breaking the material. All sizes 3/16-Inches and larger have 3 flats on the shank so that the drill chuck gets a better grip. A lubricant like water or WD-40 should be used when using these bits.