Aprilaire 10 - Replacement Water Panel for Models 110, 220, 500, 500A, 500M, 550, 558

Also fits Lennox WB2-12 bypass humidifier, the Lennox WB2-12 bypass humidifier, and the Trane THUMD300ABA00B and THUMD500APA00B humidifiers. Your humidifier water panel should be replaced at least one time per year to maintain adequate humidifier performance, or as indicated by the notification lights on your humidifier. 

Dimensions: 9-1/5" x 9-3/4" x 1-5/8"
Actual Dimensions: 9-1/5" x 9-1/5" x 1 5/8"