3M Filtrete 1000 Micro Allergen & Dust Defense Filter - 12x30x1The Filtrete Micro Allergen air filter size 12x30x1 MPR 1000 filters dust, pollen, smoke and mold spores without draining your wallet. This MERV 11 filter uses a pleated fabric with electrostatically charged fibers that act like tiny magnets to capture even the smallest particles for up to 3 months. The Micro Allergen goes to work every time your heating and cooling system kicks on. It's like having an expensive whole house air purifier, only cheaper!