Heavy Duty Disposable 23-1/2"x21"x1" Pleated Filter. This disposable filter provides protection against air debris and particles that can aggravate seasonal allergies for 2-3 months. This Heavy Duty Disposable 23-1/2"x21"x1" Pleated Filter is easy to replace. This Filter is ideal for keeping residential and even commercial grade systems clean and healthy. Be sure to replace your filter every 80-90 days to avoid any malfunctions that come with a clogged and dirty filter.