The GeneralAire 4257 is the correct replacement filter for the following air cleaner models:
The GeneralAire FP1625X5 MERV 8 AC Filter Media is a replacement air filter that fits the MAC1400 air cleaner. The GeneralAire FP1625X5 filter improves your indoor air quality by reducing particulates like dust, dander, allergens, and pollen through its MERV 8 rating. This MERV 8 filter is constructed from high capacity depth loading fiberglass media and measures approximately 16" x 25" x 5".
GeneralAire FP1625X5 MERV 8 AC Filter Media specifications: