Product review (1 stars): This is not OEM.
According to the printing on the box, it is made by Best Air Pro Replacement Part, and there is fine print that says that Best Air Pro is not affiliated with Aprilaire.

Have not tried it so don't know if it works fine or not.

<a data-hook="product-link-linked" class="a-link-normal" href="/Aprilaire-35-Water-Panel-Fits-Humidifiers-600-600A-600M-700-700A-700M-760-768-350-360-560-and-568-Pack-of-2/dp/B0076OW80S/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Aprilaire 35 Water Panel, Fits Humidifiers 600, 600A, 600M, 700, 700A, 700M, 760, 768, 350, 360, 560 and 568 (Pack of 2)</a>