3″ x 4″ Non-Woven Abrasives Hook & Loop. SurfPrep non-woven discs & pads are 3-dimensional and highly flexible. The flocked backing is to be used on SurfPrep Sanders with Hook & Loop backup pads. No vacuum holes are needed for vacuum sanding, the substrate will suck through abrasive and flocking. Make sure your vacuum is OFF when using non-woven abrasives wet for cleaning. Make sure your sander is completely dry before sanding dry materials. Blow out the sander regularly to clean out debris/material inside the tool housing.