Pentair 25022-0224S Large Outer Cartridge Replacement Sta-Rite System 3 SM-Series S7M400 Pool and Spa Cartridge Filter Large outer cartridge replacement Fits Pentair Sta-Rite System 3 SM-Series 21-inch pool and spa cartridge filter model S7M400 264-square feet filtration area Measures 19-1/4-inch length by 23-1/4-inch height by 19-1/4-inch width