Choosing a bottle may seem simple but it's not. First you need to choose the one that fits the age of the child. The bottle is also sold individually but the advice is to buy a bottle kit at least for the first time that can give you a wide choice and spare parts if necessary. One of the most recommended bottle kits is that of Avent: it is a low-end price set and contains two bottles, one of 125 ml and one of 260ml which are the capacities suitable for babies aged between 0 and 6 months. The hard plastic bottles have an ergonomic shape and above all have a double anti-colic valve. This double valve ensures that no air is formed while the baby is sucking the milk, air that would create those annoying colic and inconsolable crying that generally afflict babies up to three months of age.