Formulated of a tough, durable, and thicker gauged polyester plastic. Fasten system bolts directly to the area wall with a slide bolt assembly, making ventilation possible. Improves basement insulation. Keeps out snow, rain, and debris. Comes with brackets. Circular, Type A 40" L. x 18-1/2" W. x 9-1/2" H. Backed with a 5 year warranty.