Atoplee 3mm Straight Shank Abrasive Mounted Stone Rotary Tool Grinding Wheels Bit Set[10pcs] Shank Diameter: 3mm Grinding wheel head diameter: 4mm Good quality: 100% brand new and good quanlity, the hardness of the grinding wheelhead is high, stand wear and tear. Scope of application: mainly used for polishing or modelling on the surface of the metal and wood, or any other situation. Homogeneous granularity: the granularity of grinding wheelhead is homogeneous, the abrasive grains are not easy to fall off, so that the service life is long.