Right now there are 500 deals from Amazon Resale, formerly Amazon Warehouse Deals, in Industrial & Scientific › Filtration › Furnace Filters. These are inspected returns and open-box items that Amazon sells and ships itself. WarehouseHunter puts each one next to its current new price, so you can see what you save at a glance.

Brands with the most offers here: Nordic Pure, Filtrete, Aerostar, AIRx Filters, Amazon Basics, Filterbuy, BNX, Honeywell. Every item is a one-off, so the stock moves all day and new deals keep arriving.