Please note that some small holes on the back of cup wheel, that is Dynamic Balance Treated for cup wheel. Every cup wheel must be do Dynamic Balance before out of our factory. Diamond Segment Arrow type Design Large grinding segments with good quality steel body which provide increases durability and wheel life Dry or wet grinding of concrete, granite, stone, marble, tile, masonry and some other construction material to smooth uneven surfaces and remove flashing Suitable for any 7” angle grinders. High diamond concentration for long life and aggressive material removal.