16x25x4 (15 3/4 x 24 7/16 x 4 3/16) Filtrete Allergen Reduction Filter by 3M (2 Pack) 1550 Performance Rating Designed for housings that accommodate 4 inch nominal size filters. Captures 97% of large airborne allergens, such as pollen, mold spores and dust mite debris. Robust frame construction enhances quality and ensures high durability at the shelf. Lasts up to 12 months.