Omni CB3 Carbon Block Undersink Replacement Water Filter Cartridge 6 months or 400 gallons. This filter will not fit any Omni canisters built over 11 years ago. The factory recommends that any canister over 10 years old be changed in general for safety and performance reasons. Model no OT32, USM2, and the OB1 are ones this filter does fit. Reduces lead, cryptosporidium and giardia cysts Removes Mercury. Will not Work if the cartridge is too old. Reduces odor and chlorine,This filter is also compatible with other water filtration systems that take a 10 x 2.5 inch water filter produced by other manufacturers. Reduces rust and sediment