Amazon.com: Aprilaire 4793 Humidifier Maintenance Kit with Water Panel Model No. 10 Humidifier Replacement Filter for Aprilaire Whole Home Humidifier Models: 550, 558 : Appliances
Amazon.com: AprilAire 10 Water Panel Humidifier Filter Replacement for AprilAire Whole House Humidifier Models 110, 220, 500, 500A, 500M, 550, 550A, 558 (Pack of 1)
Troubleshooting Aprilaire humidifier - DoItYourself.com Community Forums
How to change a humidifier pad on an Aprilaire 550 humidifier. - YouTube