Merv 13 Pleated Air Filter - 11 1/2" x 21 1/2" x 1" Quantity:12-pack some just refer to them

some just refer to them as electrostatic filters

if not you can measure it or check the HVAC unit and the owner‰۪s manual

than standard fiberglass filters purchased at retail outlets

Instead of face loading (particles captured on the outer surface of the filter)

Merv 13 Pleated Air Filter - 11 1/2" x 21 1/2" x 1" Quantity:12-pack some just refer to themAny 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.