If you're sensitive to pollens and molds and want to enjoy an open window, our Window Guards are just for you. Pollen, dust and mold are kept outdoors by this unique Window Guard. Its patented triple-filtering air baffles allow only clean, fresh air to enter. It can be used in any season since it is not affected by rain, snow or high winds. Its sturdy aluminum frame makes it easy to install in any double-hung casement window. To clean, just rinse it off under running tap water. The small Window Guard is 7" high and adjusts to fit any window 20" to 36" wide. The large Window Guard is 11" high and fits any window 24" to 44" wide.