The Blue Spot Tools 125mm (5") Diamond Grinding Disc is ideal for grinding and polishing on stone, granite and marble. Suitable for use with all makes of angle grinders. Bore size 22.2mm. 5.5mm diamond segments for prolonged life. Ideal for grinding and polishing on stone, granite and marble Suitable for use with all makes of angle grinders Diameter: 125mm (5") / Bore: 22.2mm / Segment depth: 5.5 (?0.2mm) Maximum safe speed: 12250 RPM (80 m/s)