Adjustable to fit outside flue tile sizes ranging from: 8 inch x 8 inch to 13 inch x 13 inch square/rectangle and 8 inch to 12 inch round. 24 gauge powder-coated galvanized Steel hood with scalloped corners and roll-formed edges, 18 gauge 3/4 inch 100% galvanized Steel expanded metal mesh. Steel mounting clamps for easy, durable installation. Outside mounting provides greater free air space. Expanded metal mesh turned inward at base allows cover to rest firmly on flue tile, closing any openings to protect again.