These are excellent quality deburring wheels.  They are  silicon carbide rather than aluminum oxide.  The softer aluminum oxide wheels wear quickly, but these are much harder and more durable. 

They are great for cleaning up flats, and guards, and are very good for deburring. 

To use these wheels you need a bushing to reduce the 3" center hole down to the size of your arbor.  

From the Nortons website

"Norton Long Life Rapid Finish Series 1000 Wheel 8 x 1 x 3 9SF Fine 9 Density - Max RPM 4,500

Made from non-woven synthetic fiber mesh, which is impregnated with abrasives and bound with resins, non-woven wheels are designed to create desired surface finish where little or no stock removal is required. Non-woven wheels have an open mesh construction that is waterproof, washable, conformable and non-loading."