BornFree Glass Bottle - 9 oz. are made to provides mothers with the most advanced, clinically tested baby feeding systems .BornFree Bisphenol-A Free glass bottles new innovative air vent helps eliminate colic symptoms such as gas and spit-up by reducing the build up of vacuum and is also medically acknowledged to reduce the risk of middle ear infection. The unique inner valve prevents side-leaks, and unlike other vented bottles, allows you to shake freely when mixing.Each bottle comes with a level 1 nipple and a cover The Born Free feeding system is especially suitable for breast fed babies who are being introduced to bottle feeding. The unique air valve begins the steady flow of liquid when a baby starts to nurse - just like with breast feeding.The BornFree nipples are extremely soft and gentle for your baby to suckle and are available in 5 flow rates to suit babies from 0-18 months. Due to the unique BornFree valve, the nipples prevent the hard suckling needed with conventional bottles.