Naiture 2-1/4" x 10" Solid Brass Floor Register Old Victorian Style Antique Brass Finish Duct opening size: 2-1/4" x 10"(3-1/8" 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 extension from register: 3/4" which could control air flow easily by foot. To determine size needed, measure air duct opening rather than old register or grille.