The Aprilaire 4217 is the correct replacement for the following humidifiers:
The Aprilaire 4217 is a humidifier float chamber filter that works with your Aprilaire 550 and 558 model humidifiers. The Aprilaire 4217 Humidifier Float Chamber is a U-shaped component that encases the water panel inside your humidifier. This will direct any mineral deposit build up back into your water panel and out of your humidified air.
The Aprilaire 4217 Specifications:
This humidifier float chamber for your Aprilaire humidifier will keep it working at its best. By ensuring that mineral deposits stay in your water panel and out of your air, the Aprilaire 4217 elongates the life of your humidifier.