Naiture 2-1/4" x 10" Brass Floor Register Honeycomb Style In Antique Brass Finish Duct opening size:2-1/4" X 10" (3-1/4" X 11-1/8" OVERALL) Made of heavy-duty solid cast brass for durability. Finished with a durable antique brass powder coat finish to resist rust. Louver control extends 3/8" 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.