Allergy ArmorTM Ultra mattress and pillow encasings have the smallest average pore size in the industry at 2.8 microns. The fine 100% polyester fabric goes through an extra finishing process known as calendaring, in which extreme heat and pressure shrinks the pores (the gaps between the threads). These microscopic pores allow the fabric to breathe while blocking out allergenic particles. Dust mite allergen averages around 10 microns, but pet dander and mold particles may be as small as 3 microns. Allergy ArmorTM Ultra offers the comfort of luxurious microfiber bedding while keeping you safe from even the smallest allergens. A protective antimicrobial finish provides long-term protection against mold, mildew, soiling agents, stains, and deterioration.