Walmart offers the 3M Filtrete Air Micro Particle Reduction and Furnace Filter for $6.69. Opt for in-store pickup to dodge to the $5.97 shipping charge. That's $2 under our mention from a week ago, $6 off list, and the lowest price we've seen. It's available in sizes 14x20", 14x30", 16x25", 20x20", and 24x30" at this price.

Note, it's available in other sizes for $8.88 with free in-store pickup.