Product review (1 stars): Complete garbage
Believe the negative reviews for this product.  These granules clog the machine and will cause it to tell you there is no water when you have a full tank.  That alone makes the product useless and a waste of money -- these issues do not happen with the pre-assembled filters on my machine (U650).  But that's not all - they're also really aggravating and messy!

The "instructions" are a complete joke -- they're a series of IKEA-style pictograms with no additional explanation or documentation (even online - these Amazon reviews and comments appear to be the most comprehensive source of direction/discussion available).  The hardest and messiest part of the process of using these, by far, is getting the old granules out of the cartridge -- there are absolutely no instructions for that process other than that you should throw them in the garbage.  I had to scrape mine out with a kitchen knife, and after doing so for approximately 5 minutes, still had a ton of granules left that I eventually had to rinse out in the sink.  The refilling part is actually very easy.  There is absolutely no instruction to soak the cartridge after refilling, so I'm still not sure whether I'm supposed to do that or not.  At the end of the day, none of it matters since the things simply do not work and clog the filter, causing my machine to display a no water message despite a full tank (after about 20 minutes of what seemed like successful operation).

The experience of using these just underscores how much I regret paying so much money for this fancy humidifier with astronomical upkeep costs.  The simple "Safety 1st" humidifier in my son's bedroom cost a fraction of this one did, works fine (and consistently!), and doesn't require expensive replacement parts on a regular basis.