Pentair R172502J 25 Square Feet Cartridge Replacement, Pool and Spa Dynamic Series II RTL 25 Top Load High Flow Cartridge Filter Cartridge replacement Fits Pentair pool and spa Dynamic Series II top load high flow cartridge filter model RTL 25 This cartridges are manufactured of the finest quality filter media Use for spas, hot tubs, and swimming pools; available in pack of 4 Measures 4-inch length by 5-inch height by 4-inch width