OMNIFILTER CB3 ® Series C Replacement Water Filter Cartridge. Formerly TC3. IMPORTANT: DOES NOT FIT OLDER STYLE ORIGINAL AND SERIES A HOUSINGS. IF YOU HAVE AN OLDER STYLE HOUSING WE RECOMMEND THE KX PB1. Fits new style OMNI Undersink filters CBF3 and OT32, among others. 0.5 micron carbon block. Sediment, Rust, Chlorine, Lead and Mercury (harmful minerals), Cryptosporidium, Giardia Cysts, Volatile Organic Chemicals.