Two-piece frames are made of beverage board, which stays strong through humidity and temperatures with wire backed synthetic filtering media for optimal equipment protection and energy efficiency, these filters should be changed 60-90 days in periods of high use.
AF MERV 11, comparable with MPR 1200 Allergen or Micro Particle MPR800 (clean living and dust & pollen). 20X25X2 Merv 11 Pleated AC Furnace Air Filter, 4PK Made in the USA. These filters have a MERV 11 rating: Removes dust, pollen, mold, dust mites, pet dander, smoke, smog, and lint.