Naiture 4" x 10" Solid Brass Floor Register Antique Style Antique Brass Finish Duct opening size: 4" x 10" (Overall size: 5-3/4" x 11-5/8") Made of heavy-duty solid cast brass for durability. Finished with a durable antique brass powder coat finish to resist rust. Louver control extends 3/4" H from vent which could control air flow easily by foot. To determine size needed, measure air duct opening rather than old register or grille.