These Filter panels allow air exchange between any two areas which the Curtain Walls separate. The filter panels are easily removable and replaceable due to the 2" wide industrial hook & loop fasteners which are sewn directly onto both the curtain and filter panels. The 2' x 4' or 4' x 4' filter sections are reinforced via a nylon scrim pattern that allows these replaceable panels to hold their form and are the perfect way to direct air flow in curtained areas.