ARTU Glass Tile Drill Bit Unique point grinding allows for extreme low drilling pressure with excellent centering. Drill bit will not walk. Tape or center punching is no longer needed. Nice, clean holes with little to no chipping and long drill bit life. Ground double flute ensures fast and efficient removal of the drill dust and prevents clogging. The bit is ideal for drilling porcelain tiles up to a scratch hardness of 8. The unique 4-face point grinding extends the drill bit life. Drill motor must be operated at 400-600 rpm revolutions per minute . Includes pilot bit 5/32 diameter. Bit Size 5/16 , Length 4-1/2 , Type Of Tip s Cobalt and Tungsten Carbide, Shank Diameter 5/16 , Pkg Qty 1, Package Type Card