They feature the special, orthodontic, asymmetrical NUK shape, extra-wide lip support, and a new extra soft tip to fit the baby's mouth perfectly, simulating breastfeeding as closely as possible. It is so true to nature that most babies hardly notice the difference. Benefits & Features Modeled on the shape of a mother’s nipple during breastfeeding Fits all NUK first-choice bottles Anti-colic air system Suitable for medium liquid - formula milk Suitable for 0 to 6 months. How to use it? Replace teat after 1-2 months of use Sterilize bottles and teats using steam Cold water sterilization or NUK Steam Microwave Steriliser. Dishwasher sterilization is not suitable as this can cause material damage.