The Defender’s vertical bars keep the air flowing, allowing lint to pass through to minimize blockages. The Defender protects against birds and squirrels entering the dryer exhaust system. Installation is simple by placing The Defender directly over the existing external wall vent and securing it with screws. Available in two sizes, inner dimensions of 6.5” wide and 8” wide. Made in the USA from zinc coated steel with a powder coating in white, tan and brown.