The Breastfeeding Experience bottle and nipple were developed with the goal of smooth use in combination with breastfeeding and allowing babies to drink with the same mouth movements as breastfeeding. It supports a baby's proper latch and smooth tongue movements, making breastfeeding a comfortable experience. Latch-On®: the wavy line on the nipple indicates how deep a baby should latch on. This line serves as a guide for moms and dads who are unsure how deep their baby should latch on. This Latch-On® guides babies to a proper latch and supports smooth breastfeeding. Latch-on refers to the moment a mother places her nipple in her baby's mouth just as the baby begins to latch on to the mother's nipple. Once latch-on is successful, your baby and you can start breastfeeding smoothly. Nipple Size SS / S / M / L / LL.