Review on Powerful Performance: Lennox Corporation X7935 20X20X5 Filter Ensures Clean & Fresh Air by David Everett

When we replaced our oven a few years ago we made sure the new air filter was rated for this class of filter. It was 100% worth it. I just did our quarterly check yesterday and the filter was once again covered in a layer of incredibly fine gray dirt. $100 every three months seems like a fair deal if we don't have it in our lungs. Like the other reviewer, we live in Seattle and just kept the fan going with wildfire smoke for the last few weeks of summer. The air outside was terrible, but perfectly fine inside. Highly recommended - IF your system is rated for this extra filter load.