Dr browns options bottles works with or without the internal vent system in place the system continues to create 100 per cent vacuum free feeding that is clinically proven to help reduce wind related colic in your baby as their feeding develops the bottle can be used without the vent system the bottle works like a more conventional teat vented bottle making it easy and convenient for you includes 270ml wide neck bottles supplied with level 1 teat 2 150ml wide neck bottles supplie