Premium quality Carbon Block Filter Cartridge for the Twist-In Reverse Osmosis/Deionization Systems. STAGE 2 TWIST-IN CARBON BLOCK FILTER CARTRIDGE. Aquatic Life Twist-In Carbon Block Filter Cartridge: Recommend replacing every 6 months. Reduces chlorine and conditions water prior to an RO membrane. Working Pressure: Minimum 35 PSI, Maximum 80 PSI, Ideal 65 PSI
