Diamond Drill Bit Set, diameter 1/2",3/8",5/16",1/4"x3,3/16x2,1/4"Pilot drill bit x1,Round shank. Vacuum Brazed diamond technology,more efficient, more accurate and more durable. Clearly visible high quality diamond sand. The drill bit is filled with Wax Lubricant to keep it cool while drilling without the need to add water. Widely used, suitable for handgun drill and bench drill,Can be applied to Porcelain tile,Ceramic tile,Quartz stone, Glass,Ceramics,Granite,Brick,Marble,Acrylic.