Compatible with 3M Aqua-Pure AP431, HF8-S, KleenWater KW431. Interchangeable with 3M Aqua-Pure AP430, AP430SS & SF18-S Scale Inhibition System. Replace the corrosion inhibitor every 6 months to achieve effective scale inhibition effect, the specific time depends on the water condition. With continuous flow of filtered water at steady pressure and flow rates up to 10 gpm, this scale inhibitor cartridge is designed to provide water for your household needs AP431 scale inhibitor ensures you a safe water usage experience. Every efforts to improve your shopping experience. If you need assistance, including pre-order / after-sales service, please do not hesitate to contact us. 1