This Spectrum Pro Diamond Dry Core Drill Set features 5 dry cores in 127mm, 117mm, 65mm, 52mm and 38mm, as well as 6 extra accessories, all stored in a handy portable case. This set of drill bits will have you well-equipped to cut through most building materials including semi-engineering bricks, clay products and limestone aggregate concrete. The cores have a helix spiral slotted barrel for excellent dust extraction as well as turbo segments for fast, efficient drilling.