I was reading the reviews when they were talking about this mattress was thin and not good size for a twin bed, that’s correct. It was expensive for that mattress. Try to measure very good ifnot you will have a big gap in your twin bed. I will keep it because is more expensive to return it. I don’t even use it, My son is 2 years and I am afraid he will fall in this gap. I need to find another one.