PF 24sqft FNS Plus DE Filter FNS® Plus Filters feature the same, superior curved grid design as the FNS®, but with a fiberglass reinforced polypropylene body for advanced chemical resistance and superior strength. Features Superior strength Service-Ease grid pack Continuous High Flow internal air relief* 100% factory tested Top-to-bottom backwash High Flow manual air relief valve Tension Control clamp Black valves and plumbing 1-1/2in. bottom clean out port 7-1/2in. centerline bulkhead fittings