558012 Finish: Galvanized, Size: 18" x 22" Features: -Roof ventilator. -Galvanized finish. -Roof-proofed, weather proofed roof ventilators. -Include one-piece base, one-piece top with enclosed back, roll-lock seam collar and specially designed weather baffle. -Developed to provide the desired venture type opening pulls air out of the attic. -8 Mesh screen meets FHA requirements. -Screen is fastened from-head tight over opening, can"t come loose or fall out. -Base plate.