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 49-12-0062 Guard for use with a 4 inch Cup Wheel. One Cup Wheel per box.