The Teat Stays Full Of Milk, Even When The Bottle Is Horizontal, So Your Baby Can Drink In A More Natural, Upright Position. This Can Help Reduce Reflux, Aid Digestion, And Make Feeding Time More Comfortable For You And Your Little One.The Airfree Vent Is Designed To Help Your Baby Swallow Less Air. The Teat Stays Full Of Milk, Even When Horizontal, For Upright Feeding. Reducing The Air A Baby Ingests Can Help Ease Common Feeding Issues Like Colic, Gas And Reflux.