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 IRW10501918 Granite 7 piece drill bit set contains the following pieces 40 50 60 70 80 100 and 120mm