Plastic, Silicone Air vent helps reduce swallowing air. 100% leak-proof and spill-proof guaranteed. Helps make the transition from bottle to cup easier. Ultra lightweight with convenient clip for easy carrying. With a new twist on an iconic classic,feeding's glass bottle offers style on top of superior sanitising, recycling, and sustainability . The tempered glass bottle includes a classic slow flow soft silicone nipple with micro air vents to help prevent nipple collapse.