PorcelainPlus Speedbit (Tile & Glass Bit) (1/4") 3X Longer Life & 2X Faster Cutting Speed (than Conventional Carbide Bits) Recommended for use on porcelain & glass tile, granite, marble, ceramic, glass & mirrors Average of 25 seconds per hole (based on PEI Class 5 porcelain tile) Drills 10+ holes per bit (based on PEI Class 5 porcelain tile) Specially formulated carbide tip for greater durability, no walking & clean precise holes