Buy a zazen Annual Replacement Pack and be set for replacements for 12 months! Save on postage and only buy once per year. Have you reached your 5 year change over? Buy a zazen Annual Replacement Pack + Mineral Stones to have everything you need for your 5th year change over plus a spare Multi-Stage Filter Cartridge. Don't worry about remembering when to replace your spare parts - The zazen Team will email you when its time to change over !