Product review (5 stars): Perfect, Reasonably priced humidifier filter!!
I buy a 6 pack of these every year for our bedroom humidifier.  Great price vs $10 ea at the big box stores and delivered to the house!!  Prefect!!  They last 2-3 weeks if you rinse them every 2 days at least.  When they start to smell even a little bit I just trash them!!