The bottle works just like a mother's milk gland. It is equipped with an anti-colic silicone bag that contracts while your baby sucks. No air from the outside is needed to balance the vacuum created in the bottle. Therefore, there are no air bubbles, which prevents gas-related colic. Additionally, it prevents air from oxidizing the milk and destroying the nutrients, especially those in your breast milk. The bottle with the slow-flow nipple can also be used for premature babies who may not be able to suck strongly yet. The nipple is adaptable and is especially recommended for breastfed babies. The flow is proportional to the suction: it allows more or less liquid to flow out, depending on the strength with which your baby sucks. The bottle is specifically designed for combined breast and bottle feeding.