Pack of PP Options Baby Bottles, 250ml, Dr. Browns Includes: Two 250ml narrow neck bottles, two level one silicone teats (0-3 months), two internal ventilation systems consisting of 2 parts each, internal system cleaning brush, instructions. Can be used with or without the internal ventilation system Unique internal ventilation system eliminates vacuum and air bubbles to help reduce colic, expectoration, belching and gas By eliminating negative pressure it helps reduce fluid build-up in your baby's inner ear Fully ventilated design creates positive pressure, thus mimics breastfeeding and is ideal for both breast milk and formula