Product review (4 stars): Great alternative to the AC813
We buy these alternate filters for the AC813 filter.  They work just as good as the originals.  You can tell they are not made the same way but really  should be replacing these filters monthly if you use it daily.  Even the original filters tend to have the same problem where the filter is dry on the top.  We flip the filters every water fill and it works fine.  You should also clean your humidifier regularly as to not get any build up inside the base.