US Water DI Resin Cartridge 4.5" x 20" Double O-Ring Seal 1.5 GPM | USWF-4520-MB-OR Replacement Filters Carbon comes before the resin

Carbon comes before the resin on purpose: chlorine destroys softening resin

pesticides

Other companies sell you a box

up to 30% less water to drain

and other particle filtration

US Water DI Resin Cartridge 4.5" x 20" Double O-Ring Seal 1.5 GPM | USWF-4520-MB-OR Replacement Filters Carbon comes before the resinUS Water 1. 5 GPM 4. 5" x 20" Double O Ring Seal Replacement Ultra High Purity DI Cartridge For TDS Reduction Perfect for laboratories, reefkeeping and rinsing or plating operations Deionization cartridges provide solutions for a variety of applications that need the removal of ionic contaminants. Cartridges with mixed bed resins provide better than 16 megohm cm quality water for ultra pure needs. Features & Benefits Premium Mix Bed resin High