Enviroflow 18X25X1 (17.75 x 24.75) Air Filter (4 Pack) Nominal size 18x25x1, actual size 17.75 x 24.75 x 0.75 Merv 8 rated, electrostatic pleated media, which performs better than regular fiberglass fibers Traps dust and allergens such as pollen, mold, pet dander, and dust mites Pack of 4 filters Each filter lasts up to 90 days