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 (supplied with level 1 teats). 2 level 2 teats. 2 level 3 teats. Features: Dr. Browns options bottles - same trusted bottle, now with added benefits. Dr. Browns options is the first convertible bottle that can be used with or without the green vent system. The unique internal green vent system continues to create 100% vacuum free feeding, which is clinically proven to help reduce wind related colic. This is what makes 9 out of 10 healthcare professionals recommend dr browns for colicky symptoms. As baby becomes more developed the bottle can be used without the vent system to work more like a conventional, teat-vented bottle. General information: Suitable from birth.