Pentair 35505-1428 O-Ring Replacement Sta-Rite System 3 SM-Series Modular Media Cartridge Pool and Spa Filter O-ring replacement Fits Pentair Sta-Rite System 3 SM-Series modular media cartridge pool and spa filters Measures 2-1/4-inch length by 1/4-inch height by 2-1/4-inch width