The HDX Allergen Plus is made of wire-backed pleated media with a large surface area which increases the filter's dust-holding capacity and improves its efficiency. The filter's media is charged electrostatically which means it captures and traps particles that would otherwise bypass the filter. The filter has a moisture-resistant, sturdy frame and lasts up to 90-days in a typical household environment. The HDX Allergen Plus is easy to replace making change-outs quick and keeping indoor air quality at its optimal level.