The built in filter blocks pollen,, while neutralizing odors, which can keep your attic cleaner and reducing musty smells without restricting ventilation Waterproof design Performs reliably for years, even in harsh climates Reinforced Metal Backing, sagging and maintains shape under large rain, snow, or strong winds, it won ' t warps or cracks over time This vent filter easily covers most ridges vents Its flexible design allows trimming for a fit, ensuring maximums attic airflows while keeping debris out Easily Roll Out Installation: simply unrolls, cut to size, and secure with included nails; None special tools needed, Manufacturer: YPBEW