Compatible with all Medela breast pumps, easy connect adapter connects directly to breast shield;Convenient no-spill, no-leak, easy-to-close zipper top design;Protective oxygen barrier perfect for fridge or freezer;Made without BPA;Flow control valve allows baby to control milk flow;Milk only flows when baby creates a vacuum;Mimics natural feeding behavior: baby can feed, pause and breathe, similar to breastfeeding