MORE LIKE SOFT 12 INCH MATTRESS.  

Mattress is so soft you dip 5 inched. My mattress is on a day bed, the 5 inch dip has me leaning to the gap between the head rest and the bed frame. I bought the mattress 4 inch more than suggested to prevent being low. This mattress did not help me achieve that goal. 
Corners are squished in still.