Bought this mattress along with Prlage 9-inch Twin-size Smart Box Spring Mattress Foundation for my mother to sleep on when she visits. It looks and feels thick enough and firm enough to handle an adult sleeping on it without smushing down to the foundation. Granted, no one has slept on it yet, but I laid on it for a few hours and it felt great. It is not a flippable mattress, however, FYI. Would buy another if we ever needed one.