The Born Free Glass Bottle is clinically designed with leak-free Active Flow venting technology proven to reduce colic and gas for a more natural breastfeeding experience. It allows your baby to control the flow of milk. This product is free from BPA, PVC and other chemicals unsafe for your baby. Its glass is durable, eco-friendly and easy to clean. Its nipples, collars, valves and sippy cup spouts are interchangeable and applicable on all transition cups. For babies 0-3 months.