ALUMINUM, BRASS, CAST IRON, MILD STEEL, METAL, STAINLESS STEEL CUT MATERIAL; BI-METAL BLADE MATERIAL; 4-1/8 INCH DIAMETER; 120 RPM (ALUMINUM), 110 RPM (BRASS), 55 RPM (CAST IRON), 40 RPM (TOOL/STAINLESS STEEL), 80 RPM (MILD STEEL) SPEED RATING