One thing is for certain, the SandFlex Abraser is no ordinary sanding sponge. SandFlex Abrasive Blocks are made of a unique rubber compound that is impregnated with abrasive throughout the entire block. As it wears, it constantly exposes a fresh abrasive surface, self-cleans and self-sharpens. Use it like an eraser—simply rub firmly. The sanding blocks can even be carved and shaped to match contours such as for moldings or for turned bowls. They are ideal for polishing your cast iron power tool tables, chisels and plane blades, and they make incredibly quick work of shining up a stainless steel sink!