Concrete chimney cap covered with galvanized steel. Galvanized steel protects concrete from the elements and will not rust. The role of the chimney cap is to drain water and prevent it from flowing along the walls of the chimney. This will prevent damage such as infiltration into mortar joints, bricks or stones. Exterior dimensions: 26'' x 26'' Opening dimensions: 8'' 1/2 x 8'' 1/2