APEC Water ULTIMATE Series CT-24CAB is for RO-CTOP 2nd&4th stage, RO-CTOP-PH 2nd stage, and compatiable with all 10" Industry Standard Sized Countertop Water Filter System Nominal 5 Micron Rating GAC Acid Washed Carbon removes Chlorine, Odor and Taste Friction-Welded Construction Provides a Reliable, No-Leak Seal Versatile & Disposable Inline Filter Housing Design with 1/4" Quick-Connect input/output