Product review (5 stars): Culligan IC-EZ-4 EZChange water filter
The Culligan EZ4 water filter replaced an older model which had two cannisters.  The new one takes up less room and is very easy to install (under the sink) and will be easier to replace the one cartridge when necessary.  The Culligan technician was very helpful on  the phone with helping me to select the proper model.  This model is referred to for the refrigerator but I was told it is also used under the sink.