Perforated return grilles have a standard 51 percent free area on the face and can be used as a matching return in conjunction with perforated supply diffusers. Additional options include a filter frame and steel, aluminum or stainless steel construction. FEATURES AND BENEFITS Models 8R provides a smooth, perforated face that fits flush with the ceiling to blend with the room decor 3/16” staggered holes on ¼” centers 51% free area Optional opposed blade damper has screwdriver adjustment accessible through face of grille Material is steel