We recommend the regular size Bubnest. We have kept our original size (mini) as there are some babies who are born tiny and it will last them a really long time. We used the the mini with all our babies and they were all big from birth.The mini will easily last 6 months as you will be using it untied the last few months. Maxi is recommended for bubs already over 4 months old. It will fit a one year old. We also recommend this size for babies who are big from birth and who has tall parents.