New 220 Grit Black Silicon Carbide Wheel. This is a new carbide wheel. These grinding wheels are made with the finest quality graded silicon carbide grit bonded especially for lapidary work. This has 1" (25 mm) arbor hole. Plastic pop-out, step down bushings are included, which allow wheel arbor holes to adjust to 1/2" (12 mm). The wheel is especially made to give you fast, cool grinding that minimizes the risk of fracturing the material being ground. It measures approximately 6" x 1" (152 x 25 mm).