High performance dry cutting, diamond core drills. Cuts clean accurate holes with almost no breakout. For concrete block, paving slabs, limestone, clay brick and aerated block. For use with Silverline arbor and guide drill. High performance dry cutting, diamond core drills. Cuts clean accurate holes with almost no breakout. For concrete block, paving slabs, limestone, clay brick and aerated block. For use with Silverline arbor and guide drill.