Enviroflow 22X24X1 (21.5 x 23.5) Pollen and Dust Control (4 Pack) Nominal Size 22 x 24 x 1. Actual Size 21.5 x 23.5 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. Each filter lasts up to 90 days Pack of 4 Filters