Rectangular Dormer Vent is made of 26 Gauge Galvanized or Zincalume Steel. This roof Rectangular Dormer Vent is designed to provide maximum airflow into the attic; with 1-piece galvanized steel construction. Galvanized wire mesh over the opening prevents birds and large insects from entering attic space. For architectural, residential, and commercial roofing. ASTM A-653, ASTM A-792