Ambassador offers a very strong safe room of 5 1/2 inch thick steel-reinforced concrete walls and ceiling (4 inches thick) covered by studs and sheetrock. The storm room typically is configured to be a usable closet with sheetrock walls and ceiling within the home.
Other companies have advertised a similar design to be capable of withstanding an F5 tornado.
Ambassador has no grounds for making such a claim. Ambassador does however believe the room to certainly be very strong.