Product review (5 stars): Very easy replacement cartridge
There is no reason to consider any other replacement option for your Air-O-Swiss humidifier.

This is completely hassle free and is the same as what you get with the humidifier when you buy it new.  I had no issues whatsoever with this filter.  You have to soak it overnight before the first use (same as with the first one that came with the humidifier).  There's nothing else to say.  It works and it's easy and hassle-free.