Clean, Healthy Water - Reduce up to 99% of 90 contaminants including chlorine, chloramine, lead, pesticides, PFOA/PFOS, cysts, microplastics, and more from water in your house. Advanced Filtration - Replacement filter cartridges indepently tested to NSF standards 42, 53, 58, and 401. Use only certified, genuine AO Smith replacement filter cartridge for continued contaminant removal and system performance. Stage 1 and Stage 3 carbon replacement filter cartridges for AOS-HERO-CHR (B0CCQF4QZX) systems. Replace filters every six months or 365 gallons whichever comes first.