I purchased a king size to protect my 11 inch high novosbed and the protector is slightly big. This protector would definitely fit 13 inch high mattresses. I purchased this protector because my husband is a hot and sweaty sleeper no matter the season with windows left ajar. Although the mattress pad has worked so far with preventing sweat stains from seeping through, it gets pretty hot. It has only been a week but now I have been sleeping hot as well and I am a cold sleeper.