Product review (5 stars): Real Aprilaire water panels.  These are true OEM parts, not cheap "offshore" copies.
These are authentic Aprilaire water panels made by Reserch Products Corporation of Madison Wi, They are a perfect, exact replacement for the water panels supplied in new Aprilaire and Lennox humidifiers using the "Size 35" panel.  They have the same high density and coating as the original parts and work exactly the same.  Purchasing a 10-pack significantly lowers the cost per unit.  Even with the Midwest's typically highly mineral-loaded water supply, these each should last through a whole winter season as long as the water flow rate is high enough to keep the panel rinsed.  Remember to also check the in-line water strainer which should be reverse flushed each year and replaced if partially clogged or damaged.  If the in-line strainer is clogged, water flow will be slowed and the water panel will soon be covered with mineral deposits.