Compatibility: These bottles are compatible with all Medela breast pumps and Calma, allowing for seamless transition from pumping to storing and feeding using the same container. This ensures that not a single drop of precious breast milk is wasted. Leak-Proof Design: The bottles feature screw-on lids to prevent leakage when stored in the fridge, freezer, or transported during travel, providing peace of mind for breastfeeding mothers. Measurement Markings: Clear ounce and millimeter markers on the bottles make it easy to measure the exact amount of milk you have expressed, aiding in monitoring your milk supply. Convenience: These bottles minimize pouring and handling, serving as a single container for expressing, storing, freezing, and feeding breast milk, reducing washing up and simplifying the breastfeeding experience. Easy to Clean: The bottles are dishwasher and microwave safe, ensuring easy and hassle-free cleaning. Durability: Made from durable materials, these bottles are resistant to cracking or shattering when dropped, providing long-lasting use. Safe Materials: The materials used in these bottles are safe for both mothers and babies, ensuring peace of mind regarding the safety of breast milk storage and feeding. Overall, the Online Only Medela Breastmilk Bottles offer convenience, reliability, and safety for breastfeeding mothers, allowing them to efficiently manage their breast milk supply while ensuring optimal feeding for their babies.