Philips Avent Anti-colic with AirFree vent bottles are designed to reduce feeding issues: such as colic gas and reflux. The unique AirFree vent is designed to draw air away from the nipple keeping it full of milk to avoid air ingestion. This vent also keeps the nipple full of milk even when the bottle is held horizontal allowing for upright feeding. Feeding in an upright position can help to reduce reflux and aid in digestion. The nipple shape is designed for a secure latch for a comfortable feed.