Sleep Safe ZipCover's© "Secure"© box spring encasement line is made of a non woven SMS© which has the benefit of being three protective and durable layers. The result is a Secure©, durable fabric with excellent resistance to the penetration of liquids as well as having a soft, durable bed and box spring encasement that also breaths well preventing mold. It is your best solution to blocking out allergens, mites & bed bugs. This new high tech product was specifically developed to replace the heavy, off-gassing, hard to clean, vinyl material commonly used for box spring encasements.