For sale is a Lennox Powered Electrostatic Air filter 20 x 25 x 3".  Part number FC36A 1017-7.  Actual dimensions 19.875 x 24.500 x 3.000  This filter needs power to work, it is not passive. It came out of a powered air filter return plenum Model EAC3-26 (photo shown for reference only - plenum not included). 0.1 ohms between the outer two contacts. Megaohms between either outer contact and the center contact. I don't know exactly how to know if these are 100% working;  It seems to get hairy & dingy and collect dust every year, and I blow it off with compressed air to clean. If you have any questions about its measurements or function, please ask and I'll do my best to answer.