Hurricane 6" CBN Grinding Wheel, 180 Grit, 1.0" Wide, 1/2" Bore, for Sharpening High Speed Steel Tools Series II wheels are made from an aluminum core, which is lighter in weight than steel and will run smoother on all grinders Ideal for sharpening woodturning tools (High Speed Steel only) Designed for use with bench type grinders; 1800 RPM (Preferred) or 3600 RPM Wheel diameter does not change over time; CBN material is on the face and sides (1/4") of the wheel Balanced in the manufacturing process and never need "Truing" or "Dressing"