Six-sided protection against bed bugs, liquids, allergens and dust mites, Cal King, King, and Split Queen includes two pieces, Blocks bed bugs, liquids, allergens and dust mites, Rip-resistant fabric, Reliable, long-lasting fabric resists rips and tears, Zippered box spring encasement, H2Pro® Membrane allows air to permeate while blocking bed bugs, liquids, allergens, bacteria and dust mites, Three-sided zipper closure allows for simple installation