I love finding good deals on these air filters. Right now, Walmart has the Filtrete Allergen Defense Micro Particle Reduction HVAC Furnace Air Filter (Pack of 3) for only $17.88! You can choose what size you need for your home. This is a great price and a good one to stock up on. Plus, choose in-store pickup to save on shipping, or your order of $35 or more will score FREE shipping.