Cai, there is a separate "matteress" which is about 3cm thick, with a padded qilted cover that fits the base of the hammock perfectly and moulds to the curve of the hammock, so it is firm but not a hard flat base like a normal cot mattress, if that makes sense?

So when you need to tuck bub in a bit, you can tuck under the mattress, so they are really snug.