The compound shall be of the following types and grit sizes, as specified. Type I Greasemixed. Type II Watermixed . Grit 100 Coarse, for chromiumcobalt valve seats. Grit 120 Coarse, for fast valve grinding. Grit 150 Special medium coarse. Grit 180 Medium coarse. Grit 220 medium. Grit 240 Fine for chromecobalt valve seats