Universal Compatibility: Our Straw Cup Conversion Kit is specially designed to fit Dr Brown Narrow and Narrow Glass baby bottles seamlessly. The sippy cup transition kit includes 2 soft silicone Straw nipples, 2 weighted straw and 2 bottle handles, providing an all-in-one solution for your baby's transition from bottle to straw cup Smooth Transition: Our soft silicone nipple design ensures a smooth and comfortable transition for your baby from bottle to straw cup. Please note that this product is not suitable for Dr brown Wide-Neck bottles, only Narrow bottles Safety and Health: Our Straw Cup Conversion Kit is made from food-grade silicone, ensuring it's free from BPA, phthalates, and lead. We prioritize your baby's safety and well-being Installation Instructions: Begin by unscrewing the bottle nipple ring and removing the ventilation kit. Next, replace the nipple and insert the straw into it. Finally, place the bottle nipple ring and straw into the bottle, then tighten securely This product is an aftermarket item specially produced by XUNICUTE and is not affiliated with Dr Brown. If you have any questions about our product, please feel free to contact us to provide you with a solution