Aprilaire4793 Maintenance Kit for #550

AprilAire 4793 Humidifier Maintenance Kit with Water Panel Model No. 10 Humidifier Replacement Filter for AprilAire Whole-House Humidifier Models: 550, 558

AprilAire 10 Water Panel Humidifier Filter Replacement for AprilAire Whole-House Humidifier Models 110, 220, 500, 500A, 500M, 550, 550A, 558 (Pack of 2)

AprilAire 4040 Solenoid Valve, 24 Volt for AprilAire Whole House Humidifier Models 400, 400M, 500, 500M, 600, 600M, 558, 550A, 550, 568, 560A, 560, 700, 700M, 768, 760A, 760, 0.5 ounces