... corundum, look for the white, slightly higher than the hardness of corundum, easy to cut into the workpiece when grinding, good ... copper wire drawing parts, need to select the soft round of the drawing, so as not to pull the bad parts ... , recommend the use of pre-plated hardness of sand 7P No. 180 # -320 # for drawing the roun Drawing round of plating disc polisher(red)