Many moms want to have extra breast milk bottles on hand to meet their growing and changing breast milk supply. They are compatible with all Medela breast pumps and Calma, making it easy to pump, store and feed into the same container. Medela's breast milk collection and storage bottle set is a perfect complement to your breastfeeding experience. Authentic Medela spare parts are engineered, tested and approved to work specifically with your Medela breast pump. Non Medela spare parts can vary significantly in design, materials, and workmanship; all of which may affect the performance of your Medela breast pump. Made without BPA safe for mom and baby. All Medela breast milk bottles and products that come in contact with breast milk are and always have been made without BPA.