Encase® Box Spring Protector Twin Complete protection for your box spring comes from soft, durable fabric, the lab-tested H2Pro® Membrane and a zipper closure for a quiet, breathable barrier against bed bugs, liquids, allergens and dust mites. Machine washable protector is backed by a 15-year warranty. L : 20.5 - W : 20.5 - H : 9.5 - W : 17