[EXTREME HARD ]These diamond drill bits are made of industrial grade carbon steel with nickel-plated coated body to resist corrosion. A thicken diamond coating on the tops offers superior cutting strength for maximum drilling outcomes.[EXTRAORDINARY SHARP]Each diamond has a and exact finish that lower the incision resistance and drill pressure, increases the , and effectiveness of water lubrication. for making clean and precise holes on glass or ceramic and considerably extending drill bit life.[ CLEARANCE HOLE]These glass set along the drill bit facilitate the entrance of cooling water and escape of chips and other particles from drilling. Makes the drilling process easier.[WIDE USAGE] 5 size drill bits (4mm/0.16inch , 6mm/0.24inch , 8mm/0.31inch , 10mm/0.39inch , 12mm/0.47inch ) included with this glass drill bit set to meet demands. Perfect for drilling glass, tile, porcelain tile, ceramic tile, brick, and stone. length: about 2inchcolour: silverMaterial: carbon steelsize: 10x6x3cmPackage Contents: 5*Diamond Coated Drill BitAttention: keep the speed within 800-1000 per , low drill pressure and increased use of water lubrication will extend drill bit life.And keep adding water when the diamond drill bits are working on the glass or .Only the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.