CERAMIC STONES Our ceramic stones will not cup & require no lubricants, perfect for sharpening whittling & chip-carving knives which require a perfectly flat cutting edge, plus carving gouges & chisels. The secret? 94% aluminum oxide, the 2nd hardest naturally occurring composition. Black stone: medium to coarse cutting & initial shaping & sharpening, white stone: puts mirror finish, Ultra fine: final polish on a sharpened edge. Each stone is 1/2x2x8" & includes a non-slip box & instructions. Grits: MED/BLACK=600, FINE/WHITE=1,800, WHITE ULT FN=2,000+.