These pillow encasements are impenetrable to bed bugs, preventing bed bug bites while you sleep. Tests conducted by an independent entomology laboratory showed that the encasements prevented 100% of bed bugs from reaching the sleeping surface. All six interior sides of the encasement are lined with a patented polyurethane membrane that bed bugs cannot eat or slither through, preventing bed bugs from entering or forcing them to remain inside and eventually die from lack of sustenance. A patented three-sided zipper with micro teeth prevent bed bugs from penetrating the closed zipper and the patented end clasp--where bed bugs typically pass--is sealed to ensure optimal protection. The pillow encasements are 80% cotton and 20% terry cloth. Machine wash and dry. King Pillow Encasement. Set of Two. 21" W x 37" L.