Mini Grind R" uses a Type R plastic roll-on lock design as its base. Grain is fused directly to a tough polymer backing. Not paper, not cloth, not even fibre, but plastic. This one piece design prevents the risk of detaching from the holder, while the polymer promotes cool efficient grinding on WET & DRY SURFACES. Mini Grind R™ Discs outperform conventional 2 and 3 ply cloth discs. All Gemtex™Mini Grind R™ discs are powerful, versatile, flexible, safe, and economical. They are designed for use with a holder of the same size and lock system.