The Unicel FS-2005 Swimming Pool Vertical D.E. Filter Grid is for up-flow and down-flow D.E. filter systems, i.e. American, Astral, Hayward, Jandy, Pac Fab, Premier Atlas, Purex, Sta-Rite and Waterway. Unicel is the nation's leading manufacturer of swimming pool filter replacement cartridges. These filter grids are made from heavy-duty polyester and are designed to last far longer than cheaper alternatives. NOTE: PLEASE MAKE SURE THAT YOU HAVE SELECTED THE CORRECT SIZE FOR YOUR FILTER. THIS LISTING IS FOR THE 30" LONG GRID SET.