Product Features Diamond coating surface area : Almost 95%,only side is coated diamond. The laps wheels have a 1/2" arbor hole and are intended to be mechanically clamped to a master lap. Specification - 8-inch outside diameter; 1000 Grit Inner Hole Size - The flat laps wheels have a 1/2-inch arbor hole for Angle Grinder. Applicable Material - Used for grinding and polishing jewelry, glass, rock,stone, granite,etc. Flat Surface - They are absolutely flat and parallel to meet the most exacting faceting requirements. Tips - Recommended for rough and fine grinding on faceting material plus general lapidary grinding when precision is required.