This innovative 3M See-Thru™ abrasive disc provides a clear view of the workpiece as you work. This disc has a purple adhesive back that is pre-cut to the ninja shape and is easy to install. Designed for use on soft metals, the disc includes a PSA back (peel and stick) and will stick to either the cushion or hard back plate. For use with the JoolTool™ sharpening and polishing system. Each package contains 6 discs.