Zip and Block Pillow Protectors provides a protective barrier around your pillow that locks out and eliminates bed bugs, dust mites, pet dander, pollen, and mold spore allergies once and for all. A soft knit fabric with an ultra-thin breathable polyurethane membrane provides protection from allergen molecules of less than 1.0 microns. The top surface is a silky smooth polyester knit, while the bottom surface closest to the mattress is a scientifically tested breathable membrane to block out dust mites and their waste. Prevents breeding bacteria and is waterproof. Based on allergist expertise, we created the Zip & Block range of zippered mattress, box spring, pillows and duvet encasings. As medically recommended, our design is unquilted and manufactured with an outer zipper flap, an interior zipper flap and reinforced inner seams for the most effective barrier to related allergens. There is an extra long rustproof zipper for easy insertion. Zipper has both an outer and an inner flap closure for extra protection. There is a binding on inside seams for extra strength and protection. Fully-encased, provides complete coverage!