Dr Brown's Options bottle in glass 270ml/9oz twin pack comes with a level 1 teat and vent cleaning brush. It is the same trusted Options bottle that can be used with or without the vent system in order to grow with baby, plus the added attributes of glass.The unique internal green vent system creates a 100% vacuum free feeding, which is clinically proven to help reduce wind related colic. This in turn helps to reduce feeding problems, help digestion and preserve vitamins. This is what makes 9 out of 10 Healthcare Professionals recommend Dr Browns for the relief of wind related colic.Some moms and dads find removing the vent a convenient option as their baby’s feeding becomes more developed. The nipple venting creates a paced flow, and provides a feeding experience similar to most nipple-vented bottles.