Product review (5 stars): A very hard to find Type D filter
This is a very hard to find item so I was overjoyed that it was available on Amazon.  An added bonus is the Arm and Hammer baking soda infusion which further filters impurities and deodorizes the air.  A really nice feature is the color changing indicator on the side of the filter.  As we all know, the indicator gauge on the humidifier isn't accurate therefore it's not always easy to know when it needs replacement. The bright red band around the filter eliminates that guessing.  One improvement I'd make to the product is its packaging.  Since it's folded in half in the box, the filter loses its circular shape thus making it a bit fiddly to slide the square-ish filter into the round hole in the humidifier body.