Irwin IRW10501907 Granite Drill Bit 8.0 x 120mm The Irwin Granite drill bit range has been designed for impact / percussion drilling in very hard materials such as granite concrete and natural stone. They can drill 40% more holes than conventional masonry drill bits due to an extra hard thicker and more robust carbide tip. The rounded cutting edges mean higher durability resulting in 50% more accurately sized holes per drill bit. The Irwin IRW10501907 Granite drill bit has the following dimensions: Drillbit diameter: 8.0mm Total length: 120mm Working Length: 70mm