... strength :245-254N/mm^2. Our main products are granite inspection tables, squares, straight edges, square rulers, parallels, V-blocks ... bonding inserts according to customers' requirements. Our granite surface table is calibrated according to JB/T7975-1999 and ... presicion.5. non-magnetization.6. gloosy surface without sluggishness when the workplaces or tools are moving on it . black surface plate