Five 5ided® Smooth Mattress Protector Split King The Five 5ided® Smooth mattress protector helps prevent the development of asthma and features the laboratory-certified H2Pro® liquid-proof membrane on five sides of the mattress. With microscopic pores to allow air passage, the H2Pro® layer completely blocks liquids, viruses, dust mites and allergens. Unlike other bed protectors that sound like a plastic bag and don't cover the whole mattress, the Five 5ided® protector is quiet and includes the universal fit elastic ensuring a secure fit for mattress depths 6”-22”. L : 20.5 - W : 20.5 - H : 12 - W : 35