Powered 12 x 12 in this chimney cap uses 304 stainless steel for rust resistance across decades of roof top weather exposure. The welded frame and laser cut mesh screen keep rain snow leaves and small animals out of the flue while still venting smoke and combustion gases freely during fireplace use. Bird guard mesh blocks nesting birds squirrels and raccoons and the tall hood shape prevents rain from driving down into the chimney during storms.