If you want your baby to enjoy breast-like feedings then you can get Dr. Brown s Natural Flow Standard Glass Bottles. The 4 oz glass bottles feature the patented 2-piece internal vent system. This system vents out the baby bottle so that it is free from vacuum, just like breast feeding. Using this vented baby bottles for your baby helps you to minimize ingestion of air bubbles, gas, colic, and burping. They are Bisphenol-A free bottles and this makes it safe for your baby. The bottle comes in a set of 2 and also includes level one nipples. A cleaning brush is also provided with it to help make it easier for you to clean the bottle. Dr. Brown’s Natural Flow Standard Glass Bottles:Includes:Bisphenol-A free bottlesTwo 4-oz bottles with level one nipplesTwo 2-piece internal vents1 nipple cleaning brush