Three sides louvered for greater air flow. Large nailing flange. All-aluminum, rust-free construction. Fits all pitched roofs. Weathertight seamed collar. High profile for increased weather protection and circulation. Prevents roof discoloration. Birdproof. 30 sq-in of net-free ventilating area. 12-3/16 in x 17-3/4 in x 4 in overall size. Miami Dade County approved.