Silicon Carbide Flared Armor Cup Shaped Grinding Wheels has dual grit- fine grit outer rim wears slowly and eliminates waste by maintaining a flat grinding surface while the coarser grit grinds the stone, masonry or concrete. The grit is resinoid bonded. Each Cup wheel is fitted with a 5/8-11 thread molded integrally inside the cup for ready mounting on your grinder. Requires special guard. Order 49-12-0062 Guard for use with a 4 inch Cup Wheel. One Cup Wheel per box. .