GREAT BARRIER PLEATS - High temperatures and the wet environment make an unprotected filter surface a target for the growth of bacteria. Great Barrier Pleats are made with genuine Reemay Advantage with Microban. Microban protection inhibits the growth of bacteria that can cause staining odors and degradation of the filter. The unique continuous cleaning action of Microban makes the spa filter easier to clean, keeps it fresher between cleanings and ensures filter life. OD: 4 15/16\ Top ID: 2 1/8\" open Bottom ID: 2 1/8\" open Length: 13 5/16” Sq. Ft: 50"