These Hard Interface Pads are designed to be used with soft sanding discs, like the Fujistar Najimi. They have a micro hook-it Velcro attachment (standard Velcro hooks can protrude through the soft disc surface, causing surface defects on the substrate being polished). The firmness of this interface pad results in better contact with surface defects, such as dirt nibs, removing them, rather than the soft discs riding over them,