Extend the effective life of your Active Air carbon filter with a corresponding Active Air pre-filter. These pre-filters block larger particulate matter such as dust and dirt from clogging the working surface of your filter. This keeps your carbon filter operating at top efficiency for much longer. When the pre-filter becomes visibly dirty and discolored after several weeks, simply replace it. Check our large collection and find the size that matches your carbon filter. Active Air pre-filters are individually shrink-wrapped with UPC code for easy display and sale. Stock up on pre-filters to ensure you've always got the cleanest, most efficient Active Air filter in your grow room.