Don't waste your time and money on these bottles. I know they're popular but I don't know why. They leak (yes, I read the instructions, to no avail). That's not the only problem, though. On my doctor's advice, I'm adding rice cereal to my daughter's formula. As far as I can tell, Avent doesn't offer nipples suitable for cereal, so my daughter can't eat out of these bottles anymore. She sucks and sucks but can't get any cereal out of the nipples. I'm now using my Dr. Brown's exclusively. They are great. They don't leak. Also, they cut down on air bubbles, which really helps with colicy babies. Best of all, they offer a Y-shaped nipple that's perfect for cereal. If you're a new or expecting mom and are looking for a good bottle, go with Dr. Brown's, stay away from Avent.