Sta-Rite 25022-0201S Outer Replacement Module for S7M120 SM Series Filter, 200 Square Feet Large outer cartridge replacement Fits Pentair Sta-Rite System 3 SM-Series 21-inch pool and spa cartridge filter model S7M120 200-square feet filtration area Measures 19-inch length by 23-inch height by 19-inch width