Naiture 4" x 10" Steel Floor Register Victorian Style Brushed Nickel Finish Duct opening size: 4" x 10" (Overall size: 5-1/4" x 11") Made of heavy-duty, 2 mm thick steel for durability. Finished with a durable brushed nickel powder coat finish to resist rust. Removable louvers. Louver control extension from register: 5/8" which could control air flow easily by foot. To determine size needed, measure air duct opening rather than old register or grille.