The #12 Aprilaire Humidifier Replacement Water Panel is the heart of your humidifier, designed specifically to deliver the proper humidity to your home during the heating season. This product reduces pollutants from the water used by your humidifier, producing cleaner water and better indoor air quality. Replace annually for peak performance. Designed to last the entire heating season, this Humidifier Filter Water Panel will give you the best results at a great price! Order by 4pm CST for same day shipping!