The Natural Response Teat releases milk only when baby actively drinks. Babies can drink at their own rhythm like on the breast, so easy to combine breast and bottle feeding.Made of premium quality borosilicate glass, the Philips Avent glass bottle is heat and thermal shock resistant. It can therefore be safely stored in the fridge, warmed, and is also suitable for sterilization.Philips Avent's Natural Response Baby Bottles let milk flow only when your baby actively drinks. So they can drink, swallow and breathe — just like breastfeeding. It supports baby's individual drinking rhythm, through its teat features that work like a breast.The breast shaped teat is designed for a natural latch on. The wide, soft and flexible silicone teat is designed to mimic the shape and feel of a breast, helping the baby to latch on and feed comfortably. In addition, the teat has a unique opening which only releases milk when the baby actively drinks. So when they pause to swallow and breathe, the milk pauses too. With the teat opening designed to release milk only when the baby is feeding, it prevents drips, spills and loss of precious milk, so you can confidently avoid milk loss whether at home or on the go.