Temp-sensing discoloration: help parents to keep track of milk temp at any time. Purple is cold 36 96.8 , Blue is optimum feeding temperature 36-40 96.8-104 , And white is hot 40 104 . Double strong sealing: designed with double sealed side seams & double zipper to protect and freeze breastmilk. When sealing, press your fingertips and make a sound. Presterilized & bpa free thickened milk bag, safely build your milk bank. Zero contamination: milk import export separation design ensures that there is no contamination. Simply open the sealing strip when pouring milk, and cut along a cutting line when you need to breastfeeding. It's that easy space-saving design: breast milk storage bags can be freezed super flat or upright. This unique feature also allows defrost or freeze milk quickly. Friendly tips: capacity is not exceed 6oz. After milk is poured into the bag, it is necessary to release the air. After thawing, heat it to 40 c 104 f . More customers options: momcozy 200-pack breast milk storage bags are the perfect pack size to support new parents' expressing and storing in their first few months