The Aprilaire12 water panel is a genuine OEM replacement for Aprilaire whole-home humidifiers 112, 136, 224, 440, 445 and 445A, 448. When the Aprilaire 12 water panel is used with the corresponding humidifiers listed above, it is designed to last one full humidification season. However, if your home has hard water, it may need to be changed twice per season. (most times this is not the case, only in extreme circumstances) Most of these humidifiers have a maintenance light, so it will be easy to tell when your water panel needs to be replaced. The Aprilaire #12 water panel is sized at 11-1/2″ x 14-3/4″ x 1-1/2″ and is made in the USA!