Locking system. It is a product made of polyethylene. These bags do not interact with breast milk and thus maintain the quality of milk. Bags suitable for use in the refrigerator are an ideal option to keep milk fresh. In addition, thanks to the lock system on the bag, sealing is achieved and the milk is possible to store it safely. Increed Milk Storage bag is 10 pieces, a reliable and useful option for your baby's feeding.