Arbor hole :1/2 inch, 5/8 inch, 1-1/4 inch. Radius edge: 1/4 inch. ... CBN (cubic boron nitride) grinding wheels are used for sharpening woodturning tools (high speed steel HSS).The cbn grinding wheels are installed on bench grinder * Note: the small MOQ (2 pieces) and fast delivery time (5- 12 days). There will be a big discount for large orders