Pentair FNS® PLUS FILTERMore Surface Area for Better Filtration and Less Maintenance FNS Plus Filters are designed with curved grids to maximize filtration area. More filter area means better performance and longer periods between cleanings. The internal design has been refined to minimize flow restrictions and, therefore, requires minimal pumping power to achieve a needed flow rate. This vertical grid, D. E. filter is made of fiberglass reinforced polypropylene for superior