NUK Medium Flow Perfect Fit nipple provides a natural way to bottle feed your growing baby. The Perfect Fit unique nipple shape is inspired by Mom as Mom's nipple changes shape during breastfeeding and it's the same shape as the NUK Perfect Fit nipple. It provides the perfect fit in baby's mouth just like Mom, so you know that your baby will love these NUK bottles. Perfect Fit nipples are optimally sized to support baby's growing mouth and appetite, available in 2 nipple sizes and 3 flow rates. Size 1 is a smaller nipple (0 to 6 months) offered in a slow and medium flow. Size 2 is a larger nipple (6+ months) offered in fast flow. Perfect Fit nipples feature Soft Zone and Anti-Colic Air System that helps reduce colic, gas and spit-up. 1-piece vent is integrated into the nipple so there are no extra parts to clean. Soft Zone provides greater comfort as soft satiny finish conforms to baby's palate. For best results when feeding, make sure that the NUK Anti-Colic Air System symbol is under baby’s nose so that the unique drinking hole on top side is positioned correctly. BPA free and Dishwasher safe. The NUK family of brands designs safe and fun products that encourage your baby's development. NUK is committed to nurturing your children's healthy transitions from birth to toddler and has worked for over 50 years to design high quality, innovative products that are scientifically proven to support safe and healthy development.