Have ceramic and aluminum oxide abrasive grain structure superior in performance and life to standard aluminum oxides or silicon carbides. Widely used on hard metals, including hardened and mild steel, steel alloys, chrome cobalt, titanium, platinum and other ferrous metals. Also suitable for porcelain materials and wood. “CK” Stones remove material faster, run cooler, and last 3-5 times longer than other abrasives. Non-impregnating and non-contaminating. 45,000 RPM Max Speed. Made in USA.