These bottles are horrible and useless!!! They were very expensive and leaked all over the place. Ruined clothes and blankets! I have switched to Dr. Browns bottles. Cheaper and 100% better. My son (now 6 years old) had colic very bad. I wish they had the Dr. Browns bottles back then. I use them with my 4 week old and there are no air bubbles and the gas problem is almost eliminated. Thank you Dr. Brown. Shame on you Avent :( read full review »