Merv 8 Pleated Air Filter - 21 1/2" x 23 1/2" x 1" Quantity:12-pack You may know them as

You may know them as washable air or even permanent air filters

They are easy to clean by simply backwashing every month with cold water so you don‰۪t need expensive cleaners

such as dust

Unlike some permanent custom air filters

28X Increased Efficiency

Merv 8 Pleated Air Filter - 21 1/2" x 23 1/2" x 1" Quantity:12-pack You may know them asAny Kind of Filter's Extended Surface Pleated Filters outperform ordinary furnace filters with medium efficiency and are designed for lower pressure drop, and long service life which reduces HVAC equipment maintenance and energy costs. A higher MERV rating means that the air filter that you are about to purchase possesses a higher amount impurity filtration ability than your ordinary filter.