From the preemie flow nipple, which limits the flow to tiny mouths to easy-cut nipple which literally utilizes a y-shaped opening to allow for greater milk flow, you'll find the bottle nipple that's the perfect fit for your baby's feeding needs. One Size does not necessarily fit all. Keep in mind that the bottle nipple chart serves as a general guideline for choosing a bottle nipple but is by no means an end-all solution. It is important to carefully watch the feeding habits of your little one. Moving her up from a level one to a level two bottle nipple may be in order. Size chart preemie flow - for preemie babies level one - for new-borns 0+ months level two - for babies 3+ months level three - for babies 6+ months level four - for babies 9+ months easy-cut - for babies 9+ months.