14X18X1A (Actual Size) Enviroflow Air Filter (Merv 8 ) (4 Pack) Nominal Size 14x18x1. Actual Size 14 x 18 x 1 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