Whether you're remodeling an older home, adding on, building a new one, or just "fixing-up", you will be proud to own cast iron Reggio Register grilles and registers. Reggio Cast Iron Grilles and Registers have a black iron finish and are available in basically one pattern style. Note: Grilles are only a cover plate, registers are the combination of the grill and the louvers to regulate the amount of air or heat passing through it. H designates that the grilles have holes and NH designates they don't have holes.