Seamless Compatibility: This straw nipple is compatible with Dr. Brown's Narrow Baby Bottles, Glass Bottles, and Narrow Sippy Spout Bottles. No need for extra straw cups—convert your baby’s familiar bottle into a straw bottle with ease Easy Transition: The variable flow transitional nipple adapts to your baby’s sucking strength, making it ideal for babies 6 months and up to smoothly shift from bottle to straw cup and build independent drinking skills Leak Proof:Featuring advanced backflow and a spill-proof design, our straw cup nipple ensures that every sip is safe and clean. Whether at home or on the go, you won't have to worry about liquid leaking or spilling when the baby bottle is tipped over Safety and Health:Made from food-grade BPA-free silicone, this baby bottle nipple is soft and gentle, ensuring your baby enjoys a comfortable sucking experience while protecting their delicate gums. Parents can trust its safety for long-term use Easy to Clean:This replacement nipples are dishwasher and sterilizer safe.saving parents from the hassle of handwashing. Keeping the nipple hygienic and ensuring a safe drinking environment for your baby has never been easier nipples level 3