The foam sanding blocks are washable and reusable. They can be used for both wet and dry polish.Block shape should suit your specific needs, whether flat for larger surfaces or contoured for more intricate work. High-density sponge is soft, and flexible, and provides cushioning while sanding. It allows for better control and reduces the risk of leaving scratches on the surface being sanded.The sandpaper blocks come in different grit sizes, which determine the coarseness of the sanding surface. Lower grit numbers indicate a rougher surface for heavy material removal, while higher grit numbers signify finer surfaces for smoothing and finishing.