Maximum RPM is 30,000. Thin emery paper discs with pin hole centers. Excellent for smoothing and sanding metal. A natural fast-cutting abrasive, Emery, which is black silicon carbide, is glue- bonded onto these very thin Snap-On Discs. Economical and great for cleanup and finishing. 3/32" screw mandrel required. *NOT INCLUDED Flexibility Allows you to Sand Hard to Reach Areas.