31.Vacuum Brazed Diamond Drilling Bits( Parallel Shank) 32.Vacuum Brazed Diamond Drilling Bits( Thread Shank) This bit is mainly used on drill granite, marble, concrete and wall. With years of research and application of drilling bit and the world-advanced technology of diamond brazing, this products is with very free cutting, high efficiency, excellent performance and long working life. Benefits: very free cutting high efficiency excellent performance long working life Application: Drill Granite, Marble, Concrete, Wall, Other abrasive materials