Pentair 25021-0202S Small Inner Cartridge Replacement Sta-Rite System 3 SM-Series S8M150 Pool and Spa Cartridge Filter (Discontinued by Manufacturer) Small inner cartridge replacement Fits Pentair Sta-Rite System 3 SM-Series pool and spa cartridge filter model S8M150 191-square feet filtration area Measures 14-1/2-inch length by 30-1/2-inch height by 14-1/2-inch width