Filbur Pentair Hayward WW Diatomaceous Earth [DE] Grid [Partial] [18" x 9 3 4"] [36 SqFt] (FC 9430) miscelectrical and PSD90P4 compatibility give this and PSD90P4 compatibility give this part practical value because replacement cartridges work best when the new element matches the intended housing and service application closely routine skimmer performance can feel less dependable than it should and 36 square foot application give this part practical value because DE filter assemblies work best when the replacement partial grid matches the intended system family and size closely and WW applications in an 18 inch by 9 3 4 inch format for 36 square foot systems