Product review (3 stars): costly. you can get them at Marbeck cheaper
They're good but too costly.  Go to Marbeck.com and buy for just over 3 bucks each including shipping.  They're almost exactly the same filter and units work just as well. We've had these humidifiers for close to 10 yrs...Marbeck info :
"Hamilton Beach True Air humidifier filter 05900
SKU. 570-885211 12 $2.47 USD $29.64 USD