The new options8482 teats have a scalloped base which allows air to vent through the bottle when vent system is not used the teats are made from high grade super soft silicone each teat level provides a different flow ratedr browns teats level flow guidelines are58level one for feeding newbornslevel two for feeding infants aged 3 months43level three for feeding infants aged 6 months43level four for more aggressive eatersy cut faster flow for thicker liquidssuitable for dr b