Naiture 4" x 12" Solid Brass Wall Register Modern Style Chrome Finish Duct opening size: 4" x 12" (5-1/2" x 13-1/2" Overall) Made of heavy-duty solid cast brass for durability. Finished with a durable chrome powder coat finish to resist rust. Louver Control Extension from Register: 5/8" which could control air flow easily by foot. Register will have mounting holes drilled before shipping and includes two 2" screws in a matching finish. Included all the necessary mounting hardware. To determine size needed, measure air duct opening rather than old register or grille.