Aluminum Oxide Flared Cup Shaped Grinding Wheels are for General Purpose metal grinding. 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 49-12-0072 Guard for use with a 5 inch Cup Wheel. One Cup Wheel per box One Cup Wheel per box.