The Pentair PacFab FNS and FNS Plus DE Pool Filter Grids are an 8 piece set of curved grids. There are 7 full grids and 1 partial grid, which is slightly narrower than a full size grid. These Super-Pro , Unicel and/or Filbur grids can also be used with the following filters: American Products 5000 Series, American Products Titan CM, American Products Titan RMP, American Products Titan Stainless Steel, Astral 18047 Clarity DE Filter, Hayward Micro-Clear DE, Hayward Pro Grid, Jandy DEL 60 DE Filters, Pac Fab FNS (Nautilus FNS Polymeric), Pac Fab FNS Plus, Pac Fab NS (Nautilus), Pac Fab NSP (Nautilus Plus), Pentair Pool Products 5000 Series, Pentair Pool Products FNS (Nautilus FNS Polymeric), Pentair Pool Products FNS Plus, Pentair Pool Products NS (Nautilus), Pentair Pool Products NSP (Nautilus Plus), Pentair Pool Products Titan CM, Pentair Pool Products Titan RMP, Pentair Pool Products Titan Stainless Steel, Sta-Rite, Waterway Plastics Crystal Water. The 48 sq ft grids are 24” tall and the 60 sq ft grids are 30” tall. These Pentair PacFab Pool Filter Grids are used to hold up the diatomaceous earth or DE powder, which filters the water. To help with efficient filtration and ensure longer lasting grids, it is highly recommended to clean at the beginning and the end of pool season, as well as every three months for longer lasting grids. If the grids aren’t cleaned, the DE powder will not stick to the grid. This will result in clogging of the powder and the water will not be filtered correctly. It is also recommended to backwash every month or as needed to keep your pool functioning properly and looking great.