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 IRW10501908 Granite drill bit has the following dimensions:Drillbit diameter: 8.0mmTotal length: 200mmWorking Length: 130mm