This genuine replacement water panel or humidifier filter was designed and manufactured in the U.S.A. by AprilAire � the leader in indoor air quality solutions, to optimize the performance of your AprilAire whole-house humidifier models 110, 220, 500, 500A, 550, 550A, 558. For optimal performance replace water panel or humidifier filter annually. AprilAire Humidifiers can help you maintain optimal humidity in your home of 40% � 60% which has been shown to reduce the incidence of respiratory infections and symptoms related to allergies and asthma by minimizing the formation of bacteria and viruses, fungi, and dust mites. In addition, you'll feel more comfortable while also preserving items in your home susceptible to damage from changing humidity or dry conditions. Water panel dimensions: 10" H x 9.75" L x 1.75" W.