De-Ionization post filter cartridges have a mixed bed of color changing DI resin. The housing is translucent so you can see the resin color. The cartridges reduce phosphates, nitrates, silicates and TDS. Maximum of 0.25 GPM flow rate for an estimated life of 7,500 ppm. Cation and Anion DI resins 50/50. Size is 10 x 2.5 inches.