More information9mm cutting blade For cutters: A, A-1, A-3, NA-1, PA-2, 300, SPC-1, SAC-1, XA-1, SVR-1, A-5, DA -1,180-BLACK · Made of superior quality steel · All Olfa blades go through a process of adjusting hardness, sharpening angles, dimensions and other conditions in order to obtain the best balance between initial sharpening and long service life. · Difference between silver or black Excel Black blade: The traditional silver blade is somewhat less sharp but with a longer useful life and the Excel Black blade is sharper but with a slightly shorter useful life.