The Unicel FS 1002 Swimming Pool Vertical D.R. 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. They are made from heavy duty polyester and are designed to last far longer than cheaper alternatives. Unicel filters are made in the USA for the highest possible quality, allowing you to buy with confidence.