BLK210 Grinding Stone Attachment 2 x 2 x 4 (Coarse) (6 Pack)Use for grinding terrazzo, concrete, or stone. Coarse for aggressive removal of rough concrete, uneven joints, mastics, aggregate surfaces and grinding terrazzo. Medium finish grinding of concrete, stone, terrazzo, aggregate surfaces and brick. Fine smooth grinding of concrete, terrazzo, stone and brick. 6 blocks required for each machine.