12 x 5-1/4 Cast Iron Decorative Register Acorn decorative registers provide a traditional look to your home while concealing your floor and wall ducts. Acorn is the finest and largest manufacturer and distributor of forged iron builders hardware in the United States. They are dedicated to providing the highest quality products timely delivery and the most knowledgeable and courteous customer service. Outside Dimensions: 12 x 5-1/4 Inside Dimensions: 10 x 4 Includes Louver for adjusting air flow