Made up of 304-grade polished finish Stainless Steel for maximum corrosion resistance and durability, can control manual handle the opening and closing of the ventilation flap by rotating the side knob, which is convenient to use. It is very durable and long-lasting, commonly used for Marine doors, cockpit, cabin ventilation, or for household sheds. Easy to install and maintain, without modification and it is not easy to fall off, repairs can be completed in a very short period of time and hardly require any mechanical expertise. Dimensions: Diameter: 130 mm (5 inch), Thickness: 1.0 mm (0.05 inch). Package Includes 1 Pcs of MARINE CITY Stainless Steel Cabin Ventilation Plate 5 inches Round Louver Vent Cover Butterfly Air Vent Gill Plate with Side Knob.