These handy, disposable bags are used to collect, store, and freeze breast milk and are compatible with any Medela breast pump. The milk goes directly into the sterile bag, which is made of special plastic to retain the milk's beneficial properties. Each bag is equipped with a zipper top for simple storage and opening, as well as a labeling area for recording name, date, and time. These handy, disposable bags are used to collect, store, and freeze breast milk and are compatible with any Medela breast pump. The milk goes directly into the sterile bag, which is made of special plastic to retain the milk's beneficial properties. Each bag is equipped with a zipper top for simple storage and opening, as well as a labeling area for recording name, date, and time. Features and Benefits - Pump & Save breastmilk bags are designed with a double layer to minimize oxygen exposure and protect breastmilk for long-term storage. - Pre-sterilized 5oz breastmilk bags. - No-leak, easy-to-close zipper top. - No-spill, stand-up bottom. - Exclusive self-stick strap attaches directly to breastshield for fast and easy setup