Silicon Carbide Wheel 3" Diameter X 1/2" Thick X 3/8" Arbor Fine Orders over $100.00 are usually shipped within 24 hrs of receipt (excluding weekends). The estimated delivery dates showing on Amazon are usually delivered much sooner than the dates shown. Available in fine (180) and medium (150) grits. The rating on these wheels is not to exceed 8500 RPM. Free Shipping!!! Used by Professional Jewelers