Perfect Compatibility: Replaces solenoid valve in Aprilaire humidifier models 220, 224, 400, 400A, 400M, 440, 500, 500A, 500M, 550, 550A, 558, 560, 560A, 600, 600A, 600M, 700, 700A, 700M, 760, 768. Compatible with Aprilaire: 220, 224, 400, 400A, 400M, 440, 500, 500A, 500M, 550, 550A, 558, 560, 560A, 600, 600A, 600M, 700, 700A, 700M, 760, 768 Humidifiers.
eBay