Philips Avent Anti-Colic Bottle With Air Free 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. A valve in the teat prevents vacuum build-up as your baby drinks, allowing uninterrupted feeding. This can help to reduce colic, gas, spit-up and burping.