Norton Crystolon Combination Bench Stone: giant bench stone - 11½" x 2½" x 1"; coarse/fine oil stone; recommended for use on harder metals like High Speed Steel; tends to cut more aggressively but at the same time will wear more quickly.
Coarse Crystolon - 100 grit - 141 microns / Fine Crystolon - 240 grit - 53 microns