Gravity Shutter 4-Inch Black- HIPS material- Black Finish- Easy installation: The grille is easy to install and can be fitted to any wall or ceiling.- Improved indoor air quality: The grille helps to improve indoor air quality by exhausting stale air and bringing in fresh air. This can help to reduce the risk of allergies, asthma, and other respiratory problems.- Reduced moisture levels: The grille also helps to reduce moisture levels in the air, which can help to prevent mold and mildew growth.