This disposable filter for furnace and central air features a synthetic fiber filtering medium that is laminated to an expanded metal backing. This combination is then folded into an accordion pleat arrangement to increase filtering surface. It has about twice as much filtering surface area as an ordinary flat panel spun glass filter. This greater filtering surface allows more effective filtration while keeping airflow resistance low. Designed to provide allergy relief, this filter is up to 15 times more effective than spun glass on some sub-micron sized particles. Filters come in a handy 3-pack so you're set for a season. Performance level is MERV 8.