Aprilaire #10 water panel used in the models 110, 220, 500, 550, 558. These models can also be upgraded to the Honeywell antimicrobial Agion® water panel HC22E1003. This is noted on the Honeywell box.
We measured the size: 9½ x 9¾ x 1½", but the sizes may vary an 1/8".
Replace once a year. Hard water conditions may require changing twice a year. The coating will start to crumble off when in need of replacement. We have noticed with hard water that calcium deposits can build up and fall off, then end up in the furnace filter. A high quality water filter suitable for use in food service equipment is recommended.
The water panels are made of aluminum and when time to discard can be recycled. When used the coating will be loose and can be rinsed off.