Naiture 4" x 10" Steel Wall Register Victorian Style White Finish Duct opening size: 4" x 10" (5-1/4" x 11" Overall) Made of heavy-duty, 2 mm thick steel against rust. Finished with a durable white powder coat finish. Removable louvers. Louver control extension from register: 5/8" which could control air flow easily by foot. Includes tension springs for securing into wall ducts. No screws required. To determine size needed, measure air duct opening rather than old register or grille.