Bought this set of diamond cutters to grind down two 12 inch long cracks on the outside of a basement wall before caulking to prevent leaks. The 1/4" shank fits my air sander. The long shanks and different head shapes were perfect for this project. A pointed drill was used to make a small V-groove in the surface of the cracks to make them more visible. . A cylindrical drill was used to make the groove deeper and wider.And a ball drill was used to cut the grooves to set the cement for the patch.The burrs held up very well and still lasted a long time.This set of cutters was perfect for this application and would buy it again.