Aquatic Life Cartridge Mixed Bed Resin for Filtration Cation and Anion resins (H+ and OH-) remove the remaining total dissolved solids (TDS) from membrane-filtered water 10" standard size clear, refillable cartridge includes a top gasket for a secure fit Cartridge housing shape lends itself to efficient water-to-resin contact Filled with high-grade MBD-30 resin that gradually changes color as the resin is depleted New clear cartridge housing so you know when the cartridge needs to be replaced Cation and Anion resins (H+ and OH-) remove the remaining total dissolved solids (TDS) from membrane-filtered water 10" standard cartridge size includes a top gasket for a secure fit Cartridge housing shape lends itself to efficient water-to-resin contact