20X30X1 (19.5 x 29.5) Enviroflow Air Filter (Merv 8 ) (4 Pack) Nominal Size 20x30x1. Actual Size 19.5 x 29.5 x .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 Each filter lasts up to 90 days