Afirm mattress usually has a hardness of about 8 degrees. This type of mattress usually contains a soft layer such as memory foam that is not very thick, usually between 2-4cm, and then a relatively hard foam or a combination of hard foam and springs underneath. A common problem when buying mattresses online is that it is easy to sink too much when sleeping on it or sitting on the edge. If you don't like this feeling, you can choose a firm mattress.