Variflo teats are popular because they allow babies to control the flow of their milk simply by using their own sucking strength. Now for the first time and by public demand there's a Variflo Closer to Nature easi-vent teat, still with the great flex and stretch of the original award-winning teat but now available with a cross cut into the tip as well as a hole.The stronger the baby's sucking action the wider the cross opens and the faster the milk flows. It's a great teat for babies right from birth as baby is able to get as much or as little as he needs, while the easi-vent anti-colic feature on the teat's surface reduces the risk of baby swallowing air with his feed, thought to be one of the main reasons for colic. So you don't have to worry about when to change flow rates as baby knows exactly what he's doing.