I purchased the twin size and it has the same dimensions as a twin bed with the exception of thickness.  It is very comfortable as an extra bed for my grandson when he stays overnight.  He weighs 180 and says it's quite nice to sleep on.  We use two of them together because we already had one.  It doesn't expand in thickness as much as it appears to in the photo.  On a scale of 1 to 5, with 1 being firmest , it is a 4.  It is still comfortable for sleeping even without the second layer we are using.  We use the second layer to make it thick enough to for a regular twin size mattress cover and sheet.

Pros: Great value, easy assembly, durable finish.