Naiture 6" x 12" Cast Iron Floor Register Honeycomb Style Duct opening size: 6" x 12" (6-5/8" x 13-3/8" Overall) Made of 8mm-thick heavy cast-Iron with rustproof black powder coat finish for durability and reliability. Louver control extends 3/4" H from vent which could control air flow easily by foot. Removable louvers. To determine size needed, measure air duct opening rather than old register or grille.